Signaling networks have a crucial role in every aspect of plant communication with the environment. There is significant interest in identifying signal transduction pathways governing CW homeostasis in interactions with pathogens and symbionts. In previous work, our lab has demonstrated that the RAF-like Integrin-Linked Kinase 1 (ILK1) is a negative regulator of FLS2 (Flagellin Sensing2)-mediated signaling, required for defense against a low-virulence P. syringae T3SS-mutant, and modulating cellular ion homeostasis through functional interactions with Ca2+ sensor CML9 and HAK5 K+ transporter (Brauer et al., 2016). In this work we revealed that ILK1 homologs, ILK4 and ILK5, are required for plant response to PAMPs (elf18) and plant damage-associated molecules (pep1) but not flg22. Specifically, we found that ilk4 and ilk5 were unable to undergo priming for Pattern-Triggered Immunity (PTI) with elf18 and pep1 and showed increased susceptibility to virulent P.syringae pv.tomato DC3000. A global transcriptomic analysis revealed the role of ILK1 in modulating the temporal dynamics and range of Arabidopsis transcriptional re-programming postlg22 treatment. In the absence of the PAMP challenge, ilk1-1 showed derepression of a sector of PTI, osmotic and ionic stress, and iron starvation transcriptional programs. Postlg22 challenge, genes for innate immunity, microtubule (MT) structure and movement, CW biosynthesis, and plant growth were differentially regulated in ilk1-1 compared to wt. Phenotyping of ilk1-1 alongside ilk4, ilk5, and OE-ILK5 mutant lines revealed significant de-regulation of induction of defense genes, upregulation of auxin (SAURs) genes, and repression of tubulins and MT-motor protein genes. Moreover, the mutants showed abnormal insensitivity to MT-depolymerizing treatments and defective root growth and displayed CW-specific defects (i.e., ectopic lignin accumulation in the xylem and defects in the pectin-rich seed mucilage). We postulate that ILKs are components of a CW-integrity signaling pathway that suppresses PTI and facilitates CW biosynthesis during normal growth, whereas post-pathogen challenge this pathway is required for defensive re-modeling of the CW and MT cytoskeleton and resumption of plant growth.

No description available.

No description available.

Tumour cell dissemination is a major issue with the treatment of cancer, thus new therapeutic strategies which can control this process are needed. Antagonism of integrins highly expressed in tumours is one potential strategy. The integrins are transmembrane glycoprotein adhesive receptors. Two of the integrins, αVβ3 and αIIbβ3, are highly expressed in a number of tumours and induce bi-directional signalling through their interaction with extracellular matrix proteins, and growth factor receptors. Through this signalling they play an important role in a number of cellular processes that are involved in tumour dissemination such as tumour growth, migration, invasion, metastasis and angiogenesis. Dual αIIbβ3 and αVβ3 integrin antagonism will have a direct effect on β3-expressing tumour cells that leads to the inhibition of cell migration and dissemination. Furthermore, through targeting tumour cell interaction with endothelial cells and platelets, this will also lead to inhibition of angiogenesis and metastasis. The aim of this project was to characterise the expression of αVβ3 and αIIbβ3 integrin in a panel of tumour cell lines and in human tumour xenograft samples, and to develop and utilise cell-based models to investigate potential novel β3 antagonists. The expression of αV and β3 subunits was detected in xenograft tissue using immunoblotting techniques. A panel of cell lines of different tumour types including melanoma, prostate, breast, colon and non small cell lung carcinoma was then characterised for αVβ3 and αIIbβ3 integrin expression using immunoblotting and immunocytochemistry. Melanoma cell lines demonstrated the strongest αVβ3 expression. No αIIbβ3 integrin expression was seen in any of the cell lines evaluated. A selection of cell lines with varying αVβ3 expression were then used to develop a functional test for cell migration, the scratch wound healing assay. Migration of tumour cells that expressed αVβ3 integrin was inhibited by the known β3 antagonists, cRGDfV peptide and LM609 antibody. A panel of 12 potential novel β3 integrin antagonists was screened for cytotoxicity and activity in the validated scratch assay. ICT9055 was the most effective antagonist in inhibition of M14 cell migration as determined by the scratch assay, with an IC₅₀ of < 0.1 μM. Therefore the work presented in this thesis has established models and tools for evaluating potential novel β3 integrin antagonists, and identified a promising molecule to progress for further preclinical evaluation.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Background: Pancreatic ductal adenocarcinoma (PDAC), one of the fourth most lethal malig-nancies in the world, has a less than 5% five-year relative overall survival rate. Thus, there is a great need for novel therapies. PDAC is characterized as a stroma rich malignancy, composed of a large amount of extracellular matrix and pancreatic stellate cells. Accordingly, cell-matrix adhesion is crucial for cancer cell survival, invasion, and therapy resistance. We embarked on a high-throughput assay to identify the function of 117 focal adhesion proteins (FAP) in PDAC cell radiochemoresistance. Material and methods: We generated and performed a 3D tumoroid high-throughput esiRNA-based screening assay (3DHT-esiRNAs) in PDAC cell cultures (established and PDC) grown in laminin-rich extracellular matrix (IrECM). In addition to characterizing the β8 integrin expres-sion, distribution, and co-localization with other cellular organelles, such as Golgi apparatus, we also performed 3D tumoroid formation assay, sphere formation assay, type I collagen-based 3D invasion assay, and 2D clonogenic survival assay following esiRNA-mediated knockdown, 6 Gy x-ray irradiation and gemcitabine treatment. Image analysis was performed to determine Pearson's correlation coefficient, vesicle distribution and expression patterns upon irradiation or gemcitabine treatment by Fiji software (NIH). Immunoprecipitation-mass spectrometry (IP-MS) was performed to investigate the interactome of β8 integrin in the normal versus 6 Gy x-ray irradiation group. Inhibitor screen was conducted following 6 Gy x-ray irradi-ation or gemcitabine treatment to identify pathways involved in changes of β8 integrin localiza-tion upon treatment Autophagy flux was detected by monitoring LC3B puncta. Results: We identified a series of novel targets, including β8 integrin and PINCH1. Intriguingly, depletion of either β8 integrin or PINCH1 both showed radiosensitizing effect, with β8 integrin knockdown exerting a more profound radiosensitizing effect in a panel of PDAC cell lines. Without cytotoxicity, β8 integrin depletion evoked radiochemosensitization in PDAC, PDCs cell lines, and reduced sphere formation and 3D invasion into collagen-I. Intriguingly, β8 integrin was found to be located in the perinuclear region where it co-localized with the cis-Golgi matrix protein, GM130. Upon irradiation and gemcitabine treatment, β8 integrin was translocated from the perinuclear region to the cytosol, showing a slightly increased compart-mentalization in the exosome; a process that was abrogated by treatment with cytoskeletal inhibitors (paclitaxel, latrunculin B, and colchicine) and ATP synthase inhibitors (antimycin A and oligomycin). Depletion of β8 integrin influenced the autophagy via decreasing the LC3B puncta in a microtubule independent manner. Conclusion: Our results generated in 3D lrECM PDAC cell cultures, propose that β8 integrin, but not PINCH1, is a novel determinant of PDAC radiochemoresistance. Moreover, β8 integrin, although not localized to the cell membrane to facilitate cell adhesion, has a critical role in regulating intracellular vesicle trafficking under stress conditions and autophagy flux.

Tumour cell dissemination is a major issue with the treatment of cancer, thus new therapeutic strategies which can control this process are needed. Antagonism of integrins highly expressed in tumours is one potential strategy. The integrins are transmembrane glycoprotein adhesive receptors. Two of the integrins, αVβ3 and αIIbβ3, are highly expressed in a number of tumours and induce bi-directional signalling through their interaction with extracellular matrix proteins, and growth factor receptors. Through this signalling they play an important role in a number of cellular processes that are involved in tumour dissemination such as tumour growth, migration, invasion, metastasis and angiogenesis. Dual αIIbβ3 and αVβ3 integrin antagonism will have a direct effect on β3-expressing tumour cells that leads to the inhibition of cell migration and dissemination. Furthermore, through targeting tumour cell interaction with endothelial cells and platelets, this will also lead to inhibition of angiogenesis and metastasis. The aim of this project was to characterise the expression of αVβ3 and αIIbβ3 integrin in a panel of tumour cell lines and in human tumour xenograft samples, and to develop and utilise cell-based models to investigate potential novel β3 antagonists. The expression of αV and β3 subunits was detected in xenograft tissue using immunoblotting techniques. A panel of cell lines of different tumour types including melanoma, prostate, breast, colon and non small cell lung carcinoma was then characterised for αVβ3 and αIIbβ3 integrin expression using immunoblotting and immunocytochemistry. Melanoma cell lines demonstrated the strongest αVβ3 expression. No αIIbβ3 integrin expression was seen in any of the cell lines evaluated. A selection of cell lines with varying αVβ3 expression were then used to develop a functional test for cell migration, the scratch wound healing assay. Migration of tumour cells that expressed αVβ3 integrin was inhibited by the known β3 antagonists, cRGDfV peptide and LM609 antibody. A panel of 12 potential novel β3 integrin antagonists was screened for cytotoxicity and activity in the validated scratch assay. ICT9055 was the most effective antagonist in inhibition of M14 cell migration as determined by the scratch assay, with an IC50 of < 0.1 µM. Therefore the work presented in this thesis has established models and tools for evaluating potential novel β3 integrin antagonists, and identified a promising molecule to progress for further preclinical evaluation. / Public Authority for Applied Education and Training (PAAET)

No description available.

Hypercholesterolemia is a significant risk factor in the development of cardiovascular disease and is associated with chronic leukocyte adhesion in the microvasculature. While the underlying mechanisms behind this have yet to be determined, it may be possible that hypercholesterolemia impairs the fluid shear stress (FSS) inactivation of neutrophils through the rigidifying effect of cholesterol on membrane fluidity. FSS restricts surface expression of CD18 integrins through cathepsin B (ctsB) proteolysis, which minimizes neutrophil adhesivity. If hypercholesterolemia blocks FSS mechanotransduction, then the inhibition of CD18 cleavage may link pathologic blood cholesterol elevations with dysregulated neutrophil adhesion. We hypothesized that elevated cholesterol contributes to dysregulated neutrophil adhesion by impairing ctsB FSS-induced CD18 cleavage through membrane fluidity changes. In the first part of this study, we demonstrated that FSS-induced CD18 cleavage is a robust response of neutrophils and involves selective cleavage of macrophage 1-antigen (Mac1) through ctsB proteolysis. The second part of this study confirmed that ctsB regulates neutrophil adhesion through its proteolytic actions on Mac1, an important integrin involved in adhesion and chemotaxis. Specifically, ctsB accelerated neutrophil motility through an effect on Mac1 integrins during pseudopod retraction. Furthermore, by using a flow-based assay to quantify the mechanoregulation of neutrophil adhesivity, we demonstrated that FSS-induced ctsB release promoted neutrophil detachment from platelet-coated substrates and unstimulated endothelium. For the third part of this study, we linked cholesterol-related membrane fluidity changes with the ability of FSS to restrict neutrophil adhesion through Mac1. We also determined that pathologic cholesterol elevations associated with hypercholesterolemia could block FSS-induced Mac1 cleavage and were linked to disrupted tissue blood flow. This was accomplished using low-density lipoprotein receptor deficient (LDLR-/-) mice fed a high-fat diet. Ultimately, the results provided in the present study confirmed that cholesterol-related changes in membrane fluidity blocked the ability of ctsB to regulate neutrophil adhesion through FSS-induced Mac1 cleavage. This implicates an impaired neutrophil FSS mechanotransduction response in the dysregulation of neutrophil adhesion associated with hypercholesterolemia. Since dysregulated adhesion may be one of the earliest upstream features of cardiovascular disease associated with hypercholesterolemia, the present study provides a foundation for identifying a new mechanobiological factor in the pathobiology of microcirculatory dysfunction.

Small cell lung cancer (SCLC) is characterised by rapid growth, early metastatic spread and poor long-term survival. The tumour is initially sensitive to chemotherapy and thus objective response rates are high. Unfortunately, this response is often short-lived and SCLC recurs with acquired drug resistance, resulting in early patient death. Despite intensive chemo- and radiotherapy regimes survival has not improved significantly in 20 years. Prior research suggests a critical role for the tumour microenvironment in the pathogenesis of other cancers. Therefore, investigating interactions between SCLC cells and components of the tumour stroma may identify novel therapeutic targets. This thesis demonstrates that extracellular matrix (ECM) proteins present in the tumour microenvironment protect SCLC cells in vitro from chemo- and radiotherapy induced cell cycle arrest and apoptosis via cell surface β1 integrins. Pharmacological and genetic inhibition of phosphoinositol-3 kinase signalling abrogates this effect, defining a central role for this pathway in SCLC de novo drug resistance. Furthermore, the protective effect of ECM occurs without alteration in chemotherapy-induced DNA damage allowing SCLC cells to survive with new genetic defects. Integrin-mediated drug resistance has been shown to be important in other tumours and thus development of strategies to inhibit this pathway may yield new anti-cancer treatments. The design of targeted agents to down-regulate integrin-ECM interaction requires an in depth understanding of the intracellular signals that modulate integrin affinity. Two such pathways are investigated in this thesis. 1) H-Ras, a dominant suppressor of integrin affinity, acts in part through phosphorylation of Erk. Data presented here demonstrate that H-Ras also suppresses integrins through a phospholipase-C epsilon (PLCε)-dependent pathway, thus explaining discrepancies in prior data and confirming a physiological role for this recently identified phospholipase. 2) The Notch signalling pathway has been shown to have important roles in both development and cancer. It is shown here that activation of Notch signalling increases β1 integrin affinity and can protect SCLC cells from chemotherapyinduced apoptosis. However the mechanisms appear to be different; Notch-1 modulates integrin activation through the small GTPase R-Ras and Notch-2 promotes SCLC cell survival. These results define a new Notch pathway, a novel integrin modulator and a potential therapeutic target in SCLC cells. In addition to ECM proteins, the tumour microenvironment contains immune cells that may contribute to cancer growth. The cellular composition of the SCLC stroma is poorly understood. The data presented here indicate that the microenvironment of SCLC is infiltrated by lymphocytes and macrophages, the degree of which independently predicts patient survival. This suggests that the host immune system may be able to suppress SCLC growth. It is well recognised that patients with SCLC have defects in cellular immunity which correlate with survival. An in vitro coculture model was used to investigate the underpinning mechanisms, showing SCLC cells can suppress CD4+ T-cell proliferation and macrophage CD86 expression. Furthermore, preliminary data suggest a role for a soluble factor released by SCLC cells that up-regulates CD4+ T-cell production of IL-10. The work in this thesis implies a complex interaction between SCLC cells, ECM and immune cells in the tumour microenvironment. Manipulation of these pathways may have important therapeutic implications. Further investigation is required to understand the mechanisms of this interplay, which may in part be aided by prospective analysis of patient tumour samples and an in vivo model of SCLC.