Sweet potato is one of the 15 most important food crops worldwide. At least 30 different virus species, belonging to different taxonomic groups affect sweet potato. Little is known about the viruses present in sweet potato crops in Central America, which is the primary origin of sweet potato. The objective of this study was to design and implement primers for use in polymerase chain reaction (PCR) and Reverse transcription-PCR (RT-PCR) to identify and survey the diversity of plant viruses infecting sweet potato in Honduras and Guatemala. Primers were designed and used to amplify, clone, and sequence a taxonomically informative fragment of the coat protein (CP) gene for whitefly-transmitted geminiviruses (herein, sweepoviruses) and potyviruses, and of the heat shock protein 70 (HSP70) for the Crinivirus, Sweet potato chlorotic stunt virus (SPCSV). The partial genome sequences were used for identification based on phylogenetic relationships with reference sequences available in the GenBank database. All three of the plant virus groups identified in this study were found to occur either in single or in multiple infections. Results of the sequence analyses indicated that the genomic regions amplified in this study were capable of discriminating among potyvirus species, and strains of SPCSV. With respect to potyvirus, all isolates were identified as Sweet potato feathery mottle virus (SPFMV) species, except for two, which grouped phylogenetically with Sweet potato virus G (SPVG) and Sweet potato virus C (SPVC). All sweepoviruses detected in sweet potato plants belonged to a single phylogenetically, well-supported group that contains all other previously described geminiviruses (sweepoviruses) associated with sweet potato or closely related host species. These results demonstrate that the primers designed for amplification of plant virus species commonly recognized to infect sweet potato, effectively detected the viruses singly and in mixtures from symptomatic plants, and that the resultant fragment, when subjected to cloning and DNA sequenced, was phylogenetically informative at the species and/or strain levels, depending on the virus group.

HER2/neu is an oncogenic tumor-associated antigen over-expressed in several human tumors including breast and ovarian cancer. The selective expression of HER2/neu and its role in epithelial carcinogenesis makes HER2/neu an ideal target for immunotherapy. Tumor-derived chaperone-rich cell lysate (CRCL), containing numerous heat shock proteins, has successfully been used to generate tumor-specific immunity against a wide range of murine tumors and is a great candidate for an effective vaccine against HER2/neu positive tumors. In the first part of this study, the potency of human ovarian cancer-derived CRCL to activate dendritic cells (DCs) and to generate tumor-specific T cells in vitro has been investigated. Chaperone-rich cell lysate was generated from primary ovarian cancer tissues and SKOV3-A2, a HER2/neu, Wilm's tumor gene 1 (WT1) and HLA-A2 positive human ovarian tumor cell line. T cells from healthy donors and from ovarian cancer patients secreted higher amounts of interferon-γ following in vitro re-stimulation with ovarian cancer-derived CRCL compared to HER2/neu or WT1 peptide-pulsed DCs. We were also able to generate cytotoxic T lymphocyte activity against cancer-specific antigens such as HER2/neu and WT1 from all healthy donors, but from only one of the four ovarian cancer patients with bulky disease. In the second part of the study, the potency of tumor-derived CRCL to elicit the humoral immune response against a murine HER2/neu positive tumor (TUBO) has been examined. Vaccination of mice bearing a palpable tumor efficiently delayed the development of the tumor. In the vaccinated mice, CRCL vaccination induced significant anti-HER2/neu antibodies. Using B cell deficient mice and antibody transfer experiments, we have shown that the induction of anti-HER2/neu antibodies is both necessary and sufficient for the anti-tumor effect. Further, we have demonstrated that serum from TUB0 CRCL-vaccinated mice stimulated the internalization of the HER2/neu molecules, resulting in the down-regulation of their surface expression. Moreover, antibody-dependent cellular cytotoxicity has been observed against TUBO cells when presented with sera from vaccinated mice. These results indicate that CRCL may be a potent adjuvant for women suffering from HER2/neu positive ovarian or breast cancer and that this personalized vaccine may be a promising approach for active immunotherapy.

Hsp22 has been implicated in stress tolerance and longevity in various organisms though its role in Drosophila melanogaster larval thermal tolerance has not yet been investigated. I undertook this project to determine if over-expression of hsp22 in either muscle or motor neurons could alter locomotor ability at high temperature in third instar larvae of D. melanogaster. A combination of the UAS-gal4 and tet-On promoter systems was used to over-express transgenic hsp22 in the larvae. A β-galactosidase assay was used to determine the level of gene expression following administration of different amounts of tetracycline. A concentration of 100 μg/ml of tetracycline was found to elicit appreciably higher expression of the reporter gene than 0 and 0.1 μg/ml of tetracycline. Locomotor ability of larvae was assessed at a temperature of approximately 400C by measuring the time to movement failure (TMF). Larvae that were fed 100 μg/ml of tetracycline showed a significant decline in the TMF, which could be attributed to the presence of tetracycline at a concentration of 100 μg/ml. Possible reasons behind the lack of a noticeable effect of hsp22 over-expression on the TMF are discussed. The detrimental effect of tetracycline could be attributed to the decline in mitochondrial translation or a decline in the population of endogenous bacteria, which are known to exert positive effects on the development and function of Drosophila larvae. / Thesis (Master, Biology) -- Queen's University, 2007-10-01 14:24:15.801

At the cellular level, the stress response involves the synthesis of a highly conserved family of heat shock proteins (Hsps). These proteins are essential for maintenance of cellular homeostasis, both in times of stress and in normal cell functioning. Some of the most abundant forms of Hsps in the cell are members of the 70 kDa family. Intracellular heat shock protein 70 (Hsp70) expression in response to proteotoxicity is a highly conserved cellular stress response, but little is known about the role of extracellular Hsp70 (eHsp70) in fish. In order to begin characterizing eHsp70 in fish, the hypothesis that an acute stressor will elevate plasma Hsp70 levels in rainbow trout (Oncorhynchus mykiss) was tested. Subsequent in vitro studies examined whether eHsp70 level was modulated by cortisol and if this involved the action of the glucocorticoid receptor (GR), a ligand-activated transcription factor. The effect of cortisol on the eHsp70 response is important to consider because this steroid is elevated as a result of stressor exposure to allow for short-term allocation of energy stores to cope with stress. Cortisol is the primary corticosteroid in fish and exerts its main effects by binding to either GR or mineralocorticoid receptors (MR). Furthermore, eHsp70 has been previously implicated as having important immunoregulatory roles in mammalian models, but nothing has yet been reported in fish. To this end, a hypothesis tested here was that eHsp70 levels will increase after exposure to the bacterial endotoxin lipopolysaccharide (LPS), and that this response is modulated by cortisol. Finally, research on the effects of exogenous Hsp70 has not been reported in lower vertebrates; however, the relevance of this protein in intercellular signaling, especially in regards to immune regulation, is gaining increasing importance in mammalian models. Therefore, an experiment to determine whether Hsp70 would elicit upregulation of key immunoregulatory cytokines was also conducted. To accurately measure the low levels of Hsp70 in the plasma, a competitive antibody-capture enzyme-linked immunosorbent assay (ELISA) was developed. In the in vivo study, fish exposed to an acute heat shock (1h at 10°C above ambient temperature) exhibited a significant elevation in red blood cell Hsp70 levels over a 24 h period. There was also a significant increase in plasma Hsp70 levels at 4 h, but not at 24 h post-heat shock. To more specifically determine how cortisol affected the release of Hsp70, in vitro studies using primary cultures of hepatocytes demonstrated that cortisol significantly decreased eHsp70 levels in the medium at 24 h when compared with untreated controls, and this response was abolished in the presence of a GR antagonist, mifepristone (RU486). This result for the first time established a link between cortisol signaling and eHsp70 release in any animal model. When hepatocytes were exposed to LPS in vitro, eHsp70 levels were significantly lower in the LPS (30 µg/ml) group; however, heat shock abolished this effect at 24 h. Though eHsp70 levels in the heat shocked hepatocytes treated with low-dose LPS (10 µg/ml) was similar to untreated control levels, high-dose LPS treated hepatocytes showed significant elevation of eHsp70 levels above the low dose group. The ability of LPS to modulate eHsp70 release was not observed to be further regulated by cortisol. While this work suggests the modulation of eHsp70 by LPS, the physiological role remains to be elucidated. Finally when hepatocytes were exposed to exogenous Hsp70, there was no effect on key immunoregulatory genes (IL-1β and IL-8) transcript levels; however, the effect of this protein remains to be tested using other cell systems, including immune cells in fish. Overall, eHsp70 concentration was measured in trout plasma using a competitive ELISA and demonstrates for the first time that stressor exposure affects plasma eHsp70 levels in fish. Furthermore, cortisol, the primary corticosteroid in teleosts, modulates eHsp70 release in trout hepatocytes and this is action is mediated by GR signaling. Also, while trout hepatocytes secrete eHsp70 in response to endotoxin shock, a role for eHsp70 in eliciting an immune response is not clear in lower vertebrates. Taken together the results from this study suggest a role for eHsp70 in acute stress adaptation in fish, but the target tissues involved and the physiological responses remain to be elucidated. Further work on the effects of eHsp70 on target tissues effects, and the mechanisms involved, may have important implications in our understanding of the role of this stress protein in cell signaling and stress adaptation in fish.

The urokinase receptor (uPAR) plays a central role in metastatic process. It???s evident uPAR is overexpressed across a variety of tumour cells and leads to the increased aggressiveness and poor prognosis of cancer. Inhibition of uPAR expression can block metastatic potential in many tumours. In addition, besides uPA, there are several other proteins which have been confirmed to interact with uPAR, such as vitronectin and integrins. These interactions also contribute to signal transduction and the functions of uPAR complex. Therefore, downregulation of uPAR expression by targeting uPAR mRNA or protein, or by regulating the uPAR partners would be potential therapeutic strategies for prevention of cancer metastasis. There are two main aspects contained in this thesis. Firstly, three specific DNAzymes targeting uPAR mRNA were designed to downregulate uPAR expression in vitro and their effects to decrease cancer cell invasion studied in a human osteosarcoma cell line Saos-2. The results showed that two of them (Dz483 and Dz720) cleaved uPAR transcript in vitro with high efficacy and specificity and the Dz720 inhibited uPAR protein levels by 55% in Saos-2 cells. Besides, the Dz720 significantly suppressed Saos-2 cell invasion using an in vitro matrigel assay. Secondly, two potential uPAR partners from yeast two-hybrid screening, a heat shock protein MRJ and an anti-apoptosis protein HAX-1, were characterised and their functions binding with uPAR investigated. The interactions were confirmed by co-immunoprecipitation, GST-pull down assay and confocal microscopy in cancer cells. In addition, there was a 50% increase in cell adhesion after transfection with MRJ. This increase in adhesion is dependent on the uPAR/full length MRJ interaction as cells transfected with the mutant construct containing only N-terminal region or C-terminal region of MRJ had no increase in cell adhesion. The observed increase in adhesion to vitronectin by MRJ was also blocked by an anti-uPAR domain I antibody suggesting that the induced adhesion is at least in part contributed by uPAR on the cell surface. Together, the identification of both MRJ and HAX-1 as uPAR interactors provides further insight into the intricate relationship between uPAR and other proteins which may develop potential approaches for cancer therapy.

Thesis (Ph. D.)--Uniformed Services University of the Health Sciences, 2006. / Typescript (photocopy).

No description available.

Cells invest a lot of energy in order to get their proteins to fold correctly and attain functionality. It is the functional proteome of a cell that defines the ‘life of a cell’. Cells have therefore employed dedicated machinery called chaperones to enable protein folding. One class of these chaperones is heat shock proteins named so because they were initially discovered to be heat inducible and particularly important during heat stress. However the role of heat shock proteins has now been extended from merely being important for stress tolerance. Heat shock proteins are prominently involved in maintaining the correct folding and conformation of proteins and are vital in regulating the stability between protein synthesis and degradation. One of the heat shock proteins, Hsp90, is an evolutionarily conserved molecular chaperone essential in all known eukaryotes examined so far. Unlike other chaperones, Hsp90 is unique in binding to substrate proteins, which are at a late stage of folding, poised for activation by either ligand binding or interaction with other cellular factors. The most common clients of Hsp90 are signaling proteins, the classic example being steroid hormone receptors and signaling kinases. Several other proteins including transcription factors, proteins involved in cell division and development have also been shown to rely on Hsp90 functioning for their maturation. Hsp90 has emerged as an important molecular chaperone due to the large number of proteins that depend on the activity of Hsp90 for their functionality. Hsp90 plays a central role in multiple cellular processes. Since knock-out of hsp90 is lethal to most eukaryotes, inhibitors of Hsp90 have been widely used to study its function. The most widely used inhibitor is geldanamycin (GA). GA binds to the N-terminal/ATP binding site of Hsp90 which results in the degradation of client proteins. Hsp90 clients have been shown to be proteins important for diverse cellular processes such as protein trafficking, signal transduction, cell-cycle, cellular motility and development in eukaryotes. Exploring new Hsp90 clients gives an insight into more pathways that Hsp90 regulates. Intriguingly, many proteins interact with Hsp90 in a context dependent manner, i.e., under certain environmental cue, or in a particular tissue, or only under certain diseased states. It is therefore essential to study Hsp90 functioning and examine Hsp90-client interactions in more than one model organism. Dictyostelium discoideum: a model organism to study the role of Hsp90 in development The eukaryote, Saccharomyces cerevisiae that has been explored extensively for studying the diverse clientele of Hsp90, lacks various signaling pathways important for growth and differentiation as prevalent in higher eukaryotes. It is desirable to develop a model system that would combine the advantages of a lower eukaryote, in terms of its ease of manipulation and retain the complexities of higher eukaryotes. With this motivation, the social slime mold D. discoideum was explored to examine potential roles of cytoplasmic Hsp90 in growth and development. D. discoideum is ideal for studying signaling pathways important for growth and differentiation and to understand how these pathways control cellular responses to external stimuli. Multicellular development in D. discoideum occurs in response to starvation induced stress. As in case of many other protozoans, we conjectured that Hsp90 may participate in regulating developmental transition from unicellular to multicellular stages in Dictyostelium as well. My initial study attempts, to address the role of Hsp90 (HspD), in development of D. discoideum. Towards this two approaches were taken: through genetic interference of HspD, and the other, through its pharmacological inhibition. An antisense HspD plasmid was designed which upon transfection in D. discoideum, showed a very slow growth phenotype, and the cells did not survive beyond few generations. Therefore to further study the functions of HspD, I resorted to pharmacological inhibition by using the specific, well characterized inhibitor, GA. As a first step towards this I examined whether GA was capable of binding to HspD from D. discoideum cell lysate. Towards this, GA was immobilized to NHS-sepharose beads, and bound proteins were examined. Western blot of the bound fraction, using antibody specific to HspD, identified it as a predominant protein being pulled down. This was further confirmed by mass spectrometry. To be able to compare Hsp90 from D. discoideum with Hsp90s from other model organisms, HspD was cloned, purified and biochemically characterized. Comparison of ATPase activities of HspD with Hsp90’s from other systems indicates HspD to possess a relatively low ATPase activity with a Kcat of 1.6 x 10-3 min-1. The dissociation constant of GA for HspD was found to be 0.8 µM, which was in the range similar to Hsp90s from other systems. In addition, we have now obtained structural data on HspD in collaboration with crystallography groups. The N-terminal domain of HspD has been crystallized, both in -free and ligand-bound forms. Crystal structure comparison of HspD with Hsp90 from S. cerevisiae shows overall fold similarity yet some important differences in side chain orientations of specific residues in the ATP binding domain. Interestingly, on treating D. discoideum cells with GA or another Hsp90 N-terminal inhibitor, Radicicol, it was found that, while control cells progressed to develop into fruiting bodies, GA/Radicicol treated cells resulted in delayed development, and were finally arrested at the ‘mound’ stage. This suggested potential involvement of HspD in developmental progression beyond the mound stage. In order to identify the pathways that are probably affected by HspD in D. discoideum development, cells were treated with/without GA and subjected to comparative proteomics using mass spectrometric analysis. Amongst other differences, there was an obvious absence of peptides corresponding to the protein paxillin in GA treated cells. The results were verified by Western blot analysis, using a specific antibody against paxillin, wherein a drastic decrease in paxillin levels were observed in cells treated with GA. Paxillin is a key player in focal adhesion sites that functions as an adaptor protein to recruit diverse cytoskeletal and signaling proteins into a complex, and is essential for cellular proliferation and cell-substrate adhesion. My studies suggest that one of the pathways through which HspD regulates development is through cellular motility as Hsp90 was involved in regulating proteins necessary for motility and cytoskeletal organization at focal adhesion points during development in D. discoideum. Hsp90 as a target for Trypanosoma evansi infections In addition to examining the role of Hsp90 in differentiation in D. discoideum, I have also looked at the potential of Hsp90 under diseased conditions. Towards this, I explored the protozoan parasite, T. evansi, which causes a fatal disease ‘surra’. Surra is a neglected disease that mainly affects domestic and wild animals including equines, camels, cattle and buffaloes. The parasite causes significant economic losses to livestock industry. While this infection is mainly restricted to domestic (camels, equines, cattle, buffaloes, goats, sheep, pigs, dogs etc.) and wild animals, recent reports indicate their ability to infect humans. There are no reliable sensitive and specific diagnostic tests or vaccines available against this disease and the available drugs show significant toxicity. There is an urgent need to develop improved methods of diagnosis and control measures for this disease. Unlike its related human parasites T. brucei and T. cruzi whose genomes have been fully sequenced T. evansi genome sequence remains unavailable. With a view to identifying potential diagnostic markers and drug targets I have studied the clinical proteome of T. evansi infection using mass spectrometry. I have been able to identify almost 166 proteins of T. evansi, which also included potential drug and vaccine targets. Due to absence of any genome sequence information from T. evansi, most of the peptides obtained matched to its related species, T. brucei, T. cruzi and also few from Leishmania major. Importantly, I was also able to identify peptides from Hsp90. Hsp90 from T. evansi was cloned and its sequence was also obtained. To investigate the possibility of exploring Hsp90 as a target against Surra infections, TeHsp90 protein was purified by expressing it in bacterial cells, and its drug (GA) binding ability was examined in-vitro. The dissociation constant of GA for HspD was found to be 1.4 µM, which was in the range similar to Hsp90s from other systems. The ability of 17AAG (a derivative of GA) was examined in inhibiting T. evansi infection at pre-clinical level. Towards this, swiss female mice were infected with purified parasites and then the drug was injected either immediately, in one group of mice, and in another group of mice the parasites were challenged with the drug only after the onset of infection. Interestingly, both groups of mice were found to get cured using Hsp90 inhibitor. The pre-clinical results suggested that Hsp90 was an interesting drug target and its inhibitor could indeed be used against ‘surra’ infections. Hsp90 from Giardia lamblia: An unusual case Hsp90 was also examined from another pathogenic protozoan, Giardia lamblia, one of the leading causes of diarrhea in the world. Previous studies from our lab have shown Gardial Hsp90 to be coded by two different ORFs, spliced together in trans. This is indeed the only example of trans-splicing in Hsp90 known so far. My study further characterizes this finding through analysis of transcription levels of the individual ORFs, using Northern blot analysis. Importantly, I was able to detect transcripts of all three forms of Hsp90; full-length, N terminus as well as C terminus, suggesting that these are expressed and may have biological significance. To understand the significance of these independent transcripts, I have examined relative levels of expression of all three forms by Real-time PCR analysis wherein there was almost 90 fold and 5 fold lesser transcript level of N terminus and C terminus Hsp90 observed, respectively as compared to the full-length GlHsp90 expression. Previous reports have shown Hsp90 from all known organisms, to get up regulated during heat shock. Thus it was important to examine the effect of heat stress on the expression of these independent transcripts. Interestingly, different domains were found to get independently induced during heat stress. The transcript level of HspC was seen to be almost similar to that of full-length upon heat shock. There was also a significant up regulation observed in HspN transcript upon heat shock. Taking together all these observations, these results suggest a possible role for the independent domains, HspN and HspC during heat stress in G. lamblia. Furthermore, I have cloned and purified one of the individually expressed domains, HspN and characterized it biochemically. HspN was found to be able to bind to ATP, however lacked ATPase activity. Taking together all these observations, it suggests a possible role for the independent domains, HspN and HspC which needs to be investigated further. Summary Altogether, my studies establish the importance of alternate model systems in understanding the biology of Hsp90. The importance of Hsp90 was first established in growth and development of a nonpathogenic protozoan D. discoideum. My results provide significant insights into the additional pathways that Hsp90 regulates during D. discoideum development. One such important pathway was delineated to be cellular locomotion and motility. Further, I have also studied the importance of Hsp90 in neglected infectious diseases. In addition to providing a glimpse into the pathways operational during disease manifestation in T. evansi, we have shown Hsp90 to be effective in pre-clinical trials against T. evansi infections. Hsp90 from another pathogenic protozoan, G. lamblia, has also been studied. This is by far the only organism, in which there is an independent expression of the N-and C-terminal domain of Hsp90. The rare gene organization, coupled with independent expression of domains of Hsp90, makes this organism important to examine novel functions of this chaperone.

Sepsis is dysregulated host immune response to infection causing life-threatening organ dysfunction. Endothelial cell dysfunction and uncontrolled inflammatory responses are two contributors for sepsis-induced mortality. The crosstalk between endothelial and immune cells plays a critical role in the pathophysiology of sepsis. Therefore, understanding the mechanism of interaction between endothelial and immune cells will provide novel information to develop therapeutic strategies for sepsis. Pathogen associated moleculear patterns (PAMPs) and/or damage associated molecular patterns (DAMPs) produced during sepsis, activate endothelial cells to increase the expression of adhesion molecules, attracting immune cell infiltration into the tissues. Uncontrolled inflammatory responses during the early phase of sepsis contribute to organ failure and lethality. Over 100 clinical trials, targeting inflammatory responses in sepsis, have failed in the past three decades. Thereby, developing novel therapeutic strategies for sepsis are urgent. Heat shock protein A12B (HSPA12B), as one member of HSP70 family, predominately expressed in the endothelial cells, plays important roles in many pathophysiological processes. Currently, we observed endothelial cell specific HSPA12B deficiency (HSPA12B-/-) exacerbates mortality in sepsis induced by cecal ligation puncture (CLP). HSPA12B-/- septic mice exhibits increased expressions of adhesion molecule and infiltrated macrophages in the myocardium and activated macrophages in the peritoneal cavity. In vitro studies show that HSPA12B could be secreted from endothelial cells via exosome. HSPA12B carried by exosomes can be uptaken by macrophages to downregulate macrophage NF-kB activation and pro-inflammatory cytokine production. Trained immunity, induced by β-glucan, causes immune memory in innate immune cells, with an altered response towards another challenge. We have found that mice received β-glucan seven days before CLP sepsis exhibit attenuated mortality with decreased pro-inflammatory responses. We found that β-glucan significantly increased the levels of HSPA12B in endothelial cells and endothelial exosomes. β-glucan induced endothelial exosomes markedly suppress macrophage NF-kB activation and pro-inflammatory responses. The current data suggests that HSPA12B plays a novel role in the regulation of immune and inflammatory responses and that HSPA12B could be an important mediator for the crosstalk between endothelial cells and macrophages during sepsis. β-glucan regulates endothelial cell functions and immune/inflammatory responses, thus improving survival outcome in CLP sepsis.

Heart failure after myocardial infarction (MI) remains the leading cause of mortality among all cardiovascular diseases globally. Angiogenesis plays a critical role in cardiac functional recovery after MI. Heat shock protein A12B (HSPA12B) is predominately expressed in endothelial cells and required for angiogenesis. Yes-associated protein (YAP) has been reported to promote tumor angiogenesis. In the present study, we investigated the cooperative role of HSPA12B and YAP in angiogenesis following myocardial ischemic injury. Endothelial specific deficiency of HSPA12B (eHspa12b-/-) or YAP (eYap-/-) impairs angiogenesis and exacerbates cardiac dysfunction after MI, when compared with wild type (WT) mice. In addition, MI induced angiogenesis and the expression of angiogenic factors (angiopoietin-1, VEGF and VEGFR2) were impaired in both eHspa12b-/- and eYap-/- hearts. MI increased YAP expression and nuclear translocation in WT hearts, but not in eHspa12b-/- myocardium. Similarly, MI also markedly increased HSPA12B expression and nuclear translocation in WT mice but not in eYap-/- hearts. In vitro data shows that overexpression of HSPA12B upregulated hypoxia induced endothelial cell proliferation, migration and angiogenesis. On the contrary, deactivation of YAP by verteporfin attenuates endothelial cell proliferation, migration and angiogenesis after hypoxic challenge. In accordance, silencing of either HSPA12B or YAP suppressed endothelial cell proliferation and angiogenesis promoted by hypoxia. Importantly, YAP inhibition abrogates HSPA12B induced endothelial cell proliferation and angiogenesis. Deficiency of HSPA12B suppresses YAP expression and nuclear translocation following hypoxia while knockdown of YAP attenuates hypoxia stimulated HSPA12B expression and nuclear translocation. Mechanistically, hypoxia induced an interaction between endothelial HSPA12B and YAP. Of note, ChIP assay shows that HSPA12B is a target gene of YAP/transcriptional enhanced associated domain 4 (TEAD4). Further investigation indicates that HSPA12B also acts as a co-activator in YAP associated proliferation and angiogenesis. HSPA12B can stabilize YAP and prevent YAP from degradation. Therefore, our results delineated a previously unrecognized role of endothelial HSPA12B as a novel target and co-activator for YAP/TEAD4 and cooperates with YAP to promote endothelial cell proliferation, migration and angiogenesis following myocardial ischemia.