G-protein coupled receptors (GPCRs) have been shown to interact with an array of accessory proteins that modulate their function. I hypothesize that the GLP-1R, a B-class GPCR, similarly has interacting proteins that regulate its signaling. An unliganded human GLP-1R was screened using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay and a human fetal brain cDNA prey library to reveal 38 novel interactor proteins. These interactions were confirmed by co-immunoprecipitation and immunofluorescence. When co-expressed with the GLP-1R in cell lines, 15 interactors significantly attenuated GLP-1-induced cAMP accumulation. Interestingly, SiRNA-mediated knock down of three selected novel interactors, SLC15A4, APLP1 and AP2M1, significantly enhanced GLP-1-stimulated insulin secretion from the MIN6 beta cells. In conclusion, this present work generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling; and the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.

G-protein coupled receptors (GPCRs) have been shown to interact with an array of accessory proteins that modulate their function. I hypothesize that the GLP-1R, a B-class GPCR, similarly has interacting proteins that regulate its signaling. An unliganded human GLP-1R was screened using a membrane-based split ubiquitin yeast two-hybrid (MYTH) assay and a human fetal brain cDNA prey library to reveal 38 novel interactor proteins. These interactions were confirmed by co-immunoprecipitation and immunofluorescence. When co-expressed with the GLP-1R in cell lines, 15 interactors significantly attenuated GLP-1-induced cAMP accumulation. Interestingly, SiRNA-mediated knock down of three selected novel interactors, SLC15A4, APLP1 and AP2M1, significantly enhanced GLP-1-stimulated insulin secretion from the MIN6 beta cells. In conclusion, this present work generated a novel GLP-1R-protein interactome, identifying several interactors that suppress GLP-1R signaling; and the inhibition of these interactors may serve as a novel strategy to enhance GLP-1R activity.

Advanced melanoma poses a major therapeutic challenge, and despite the development of recent promising therapeutic agents, resistance to treatment remains a problem. Until recently, despite low response rates, alkylating agents dacarbazine and temozolomide (TMZ) were the standard of care for the treatment of advanced melanoma. The cytotoxic effects of these agents relies upon the formation of alkylated base lesions such as O⁶-methylguanine (O⁶MeG), which is repaired by a protein implicated in TMZ resistance called O⁶-methylguanine-DNA methyltransferase (MGMT). Failure to resolve such alkylated bases results in DNA replication-associated double-strand breaks (DSBs). The type 1 insulin-like growth factor receptor (IGF-1R) mediates a number of characteristics common to cancers, including proliferation and survival, and evidence suggests it may also contribute to resistance to many anticancer agents. The aims of this study were to test whether melanoma cells could be sensitized to TMZ by small molecule IGF1R inhibitors, and to explore the mechanism of any chemosensitization. This study found an association between basal IGF1R phosphorylation and in vitro TMZ resistance in seven MGMT-proficient melanoma cell lines, suggesting that IGF1R activation may be linked with TMZ resistance. Furthermore, IGF1R inhibition caused dose-dependent sensitization of melanoma cells to TMZ, regardless of BRAF mutation status. This reduction in cell survival was not accompanied by an increase in apoptosis, but rather Chk2 activation and an accumulation of cells in the G2/M phase of the cell cycle, suggesting a possible effect of IGF1R inhibition on DNA repair. IGF1R depletion was found to increase MGMT protein levels and activity, but this effect was not seen in IGF1R inhibited cells. In addition, IGF1R inhibition was not epistatic with MGMT inhibition, and IGF1R inhibition reduced survival of TMZ treated MGMT-null cells. This suggested that TMZ sensitization by IGF1R inhibition was independent of MGMT. IGF1R inhibition did however cause an increase in the accumulation of TMZ-induced RPA foci, and delay in resolution of RAD51 foci. Together with the finding that IGF1R inhibition reduced survival in PARP inhibited melanoma cells, these results suggested that IGF1R inhibition influenced DSB repair by homologous recombination. Finally, the combination of IGF1R inhibition with TMZ was tested in a mouse model and was found to be tolerable. TMZ or IGF-1R inhibitor alone caused minor reduction in melanoma xenograft growth rates (rate reduction by 13% and 25% respectively), while combination treatment caused supra-additive growth delay (72%) that was significantly different from other treatment groups (p<0.05). The findings of this study suggest IGF1R inhibition as a possible option in overcoming alkylating drug resistance in melanoma.

The sigma-1 receptor (σ-1R) is an endoplasmic reticulum (ER) protein that modulates a number of ion channels. It is hypothesized that σ-1Rs activated with agonist translocate to the plasma membrane. The σ-1R potentiates N-methyl-D-aspartate Receptors (NMDARs), important constituents of synaptic plasticity. NMDARs are anchored in the plasma membrane by Postsynaptic Density Protein-95 (PSD-95). The mechanism behind σ-1R modulation of NMDARs is not known. The results of my investigation confirm that σ-1Rs localize extrasomatically. Following σ-1R activation, σ-1R localization to dendrites and postsynaptic densities (PSDs) is upregulated. Unpublished work from our lab has shown that σ-1Rs associate with PSD-95 and NMDARs. Furthermore, immunocytochemistry (ICC) showed σ-1R colocalization with PSD-95 and NMDAR subunits. After σ-1R activation there was significantly increased colocalization between σ-1R, PSD-95, and GluN2B. Overall, this study may have provided insight into the molecular mechanism behind σ-1R modulation of NMDARs, which could have implications in the understanding of synaptic plasticity.

Environmental factors such as ambient temperature and oxygen availability are variation in different altitude. Individuals within a species, living in variable environments often display phenotypic plasticity by changing morphology, behavior, reproduction, and physiology to meet the individual¡¦s ability to survive demanding conditions. This study was aimed to investigate the expression of angiotensin receptor and nitric oxide synthase genes of individuals resided at differential altitude, in an attempt to find the role of these molecules in cardiovascular adaptation to altitude. Spiny rats (Niviventer coxingi) are widely elevational distributed in Taiwan. They were studied under more natural conditions to provide an ecological context data on physiological plasticity between the different altitudes. I examined the body weight, blood pressure, heart rate and the expression of angiotensin type 1 or type 2 (ATI or ATII) receptor and nitric oxide synthase (NOS) genes in tissues (cortex, hypothalamus, medulla, lung, heart, aorta, adrenal gland and kidney) of spiny rats resided at differential altitude and during the domesticated period. The results of the study showed that spiny rats resided at higher altitudes were lighter than that at lower altitudes (750 m: 178.6¡Ó35.8 g and 1600 m: 122.3¡Ó29.3 g). Spiny rats resided at 1600 m did not change their body weight during the domesticated period, but rats resided at 750 m gradually reduced their body weight. Blood pressure and heart rate were similar between rats resided at different altitudes, and did not change during the domesticated period. ATI receptor, endothelelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS) mRNA expression in these tissues were similar between rats resided at different altitudes. ATII receptor mRNA expressed in these tissues under our detection limit. Rats resided at 750 m declined the level of nNOS in heart, when they were domesticated at 100 m. ATI receptor in kidney reduced at first, but subsequently increase to same level like native. Moreover, rats resided at 1600 m declined the level of iNOS in heart, when they were domesticated at 100 m. Together, these results indicate that heart rate, blood pressure, ATI receptor, eNOS, iNOS and nNOS mRNA expressions in these tissues were similar between rats resided at different altitudes. If there was no other compensatory mechanism, individuals resided at higher altitude were limited in low available oxygen. A reduced body weight could help in adaptation to high-altitude.

Previous studies show that coronary artery disease (CAD) is a multi-factors and chronic inflammatory disease, and is associated with lipid metabolism. IL-1ra is a naturally occurring anti-inflammatory molecules that block the action of IL-1. However, little is known about the imbalance between IL-1ra and inflammatory mediators in CAD. We attempted to investigate the relationships between inflammatory mediators and serum IL-1ra levels in patients with CAD. In 95 patients with angiographically defined CAD, and 70 healthy controls were studied in a case-control manner. Serum levels of cytokines and the risk factor of CAD were examined. Polymorphisms for IL-1ra gene were detected by PCR, and genotypes and allelic frequencies in both groups were compared. Our major finding include: (1) The risk factors such as elevated BMI, systolic BP, smoking, hypertension, blood glucose, and TG was more frequently found in the CAD group than the control group ( p < 0.001). However, the HDL-C and bilirubin were significantly higher in control group than the CAD group. (2) The relative risk of those in the highest quartile of ratio of LDL-C to HDL-C, TC to HDL-C, and TG to HDL-C were significantly elevated. ( OR = 2.98, p < 0.01; OR = 5.31, p <0.001; OR = 8.43, p < 0.001 respectively) (3) Five different inflammatory markers were significantly elevated including IL-1ra, hs-CRP, IL-6, leukocyte count, and neutrophil percentage between healthy controls and CAD patients. ( p < 0.01) (4) Levels of IL-1ra and other variables such as blood glucose, BMI, TG, IL-6, hs-CRP, and leukocyte count has significantly correlated, and were inversed correlation in bilirubin, and HDL-C in all study subjects. ( p < 0.01) (5) In the multiple logistic regression analysis, adjustment was made for variables. The relative risk of CAD for the highest quartile of IL-1ra, as compared with the lowest quartile, had an Odds ratio 2.57 ( 95% confidence intervals, 1.12 - 5.91, p = 0.026 ) increase in risk for CAD. (6) Similar results were obtained hs-CRP, IL-6 in the highest quartile were increase risk for future CAD. ( OR = 5.86 and 5.79 respectively; p < 0.001) (7) The join effect cytokines of hs-CRP, IL-6, IL-1ra concentrations may play important role in CAD risk. ( OR = 10.19, p < 0.001 ) (8) In addition, IL-1ra allele 2 genotype and allelic frequencies were no significant association with increase in IL-1ra with CAD. In conclusion, we find a significant association of elevated IL-1ra levels in the patients with CAD. Thus, these results support the hypothesis that inflammation, anti-inflammation cytokines and lipoprotein metabolism provide a useful marker for predicting the development of CAD events.

IL-1 is an essential pro-inflammatory factor in inflammation response. The effect of IL-1 is through binding to the IL-1 receptor that triggers the following signal transduction pathway. To study the role of IL-1 receptor-mediated signal pathway in inflammatory response, injecting P. aeruginosa into trachea of wild-type (WT) and type-1 IL-1 receptor knock-out (IL-1R1-/-) mice was used as the experimental model. Injecting bacterium into trachea of mice will induce pneumonia which increases accumulation of neutrophils, production of nitric oxide, expression of intercellular adhesion molecule-1 as well as many kinds of cytokines and causes the lung damage. The pneumonia-induced lung damage and inflammation at 24 hr after injecting P. aeruginosa into trachea were more severe in knock-out than in WT mice, as demonstrated by increases in extravasations of Evans blue dye (EBD), myeloperoxidase (MPO) activity, expression of iNOS, IL-1 beta and ICAM-1, and higher mortality of knock-out mice. The cause of the high mortality in knock-out mice was further investigated by culturing the lung and blood samples for bacterial counts. The bacterial counts of lung and blood of IL-1R1-/- mice were all higher than that of WT mice in 8 to 24 hr after injection of bacterium. Finally, chimeric mice (WT ¡÷ WT, IL1R1-/- ¡÷IL1R1-/-, WT ¡÷ IL1R1-/-, IL1R1-/- ¡÷ WT) were generated and used to determine the role of PMN cells of blood. Suggesting that increased amounts of bacteria in lung and blood is related to the higher mortality in knock-out mice and the type-1 IL-1 receptor is essential for mice to against pneumonia in this model.

The sigma-1 receptor (σ-1R) is an endoplasmic reticulum (ER) protein that modulates a number of ion channels. It is hypothesized that σ-1Rs activated with agonist translocate to the plasma membrane. The σ-1R potentiates N-methyl-D-aspartate Receptors (NMDARs), important constituents of synaptic plasticity. NMDARs are anchored in the plasma membrane by Postsynaptic Density Protein-95 (PSD-95). The mechanism behind σ-1R modulation of NMDARs is not known. The results of my investigation confirm that σ-1Rs localize extrasomatically. Following σ-1R activation, σ-1R localization to dendrites and postsynaptic densities (PSDs) is upregulated. Unpublished work from our lab has shown that σ-1Rs associate with PSD-95 and NMDARs. Furthermore, immunocytochemistry (ICC) showed σ-1R colocalization with PSD-95 and NMDAR subunits. After σ-1R activation there was significantly increased colocalization between σ-1R, PSD-95, and GluN2B. Overall, this study may have provided insight into the molecular mechanism behind σ-1R modulation of NMDARs, which could have implications in the understanding of synaptic plasticity.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 4 uppsatser.

Thesis (M.Sc.). / Written for the Dept. of Biochemistry. Title from title page of PDF (viewed 2008/05/29). Includes bibliographical references.