Signal-transducing G proteins: basic and clinical implications

The genetic variant C825T of the beta 3 subunit of G protein is associated with hypertension in a Portuguese population

INTRODUCTION

Hypertension is an important public health problem, affecting about 25% of the adult population worldwide.1 Genetic and environmental factors contribute to its pathogenesis. The T allele of the C825T polymorphism of the beta 3 subunit of G protein (rs5443) leads to the production of a truncated variant that enhances intracellular signaling and may interfere with the regulation of blood pressure. This genetic variant has been described as a risk factor for hypertension, although study results are controversial.

OBJECTIVE

The objective of this study was to analyze the association of the C825T polymorphism of the GNB3 gene with the occurrence of hypertension in a Portuguese population from the Madeira archipelago.

METHODS

A case-control study was performed with 1641 Caucasian individuals (mean age 50.6±8.1 years), 848 with hypertension and 793 controls. Blood was collected from all participants for biochemical and genetic analysis, including genotyping of the C825T polymorphism. Logistic regression analysis was performed to determine which variables were significantly associated with the onset of hypertension. Statistical analyses were performed using IBM SPSS version 19.0 and p-values <0.05 were considered statistically significant.

RESULTS

In our study, there was a significant association between the C825T polymorphism of the GNB3 gene and the occurrence of hypertension (odds ratio 1.275; 95% confidence interval 1.042-1.559; p=0.018) in the dominant model, after multivariate analysis.

CONCLUSION

We conclude that the C825T polymorphism of the beta 3 subunit of G protein is significantly and independently associated with the occurrence of hypertension in the study population.

The interaction of thrombin with blood platelets

Thrombin is a potent agonist of platelets. In the current article, the research on the interaction of thrombin with blood platelets is reviewed starting with the first studies demonstrating the direct action of thrombin on platelets and ending with an analysis of the importance of the protease-activated receptors (PARs) and the GpIb complex. The antithrombin activity of platelets is discussed in terms of the binding of thrombin to receptor(s) on the platelet surface. Evaluation of the PAR receptors and the GpIb supports a model where thrombin binds to the GpIb receptor prior to the proteolysis of the PAR receptor(s). Thus, the maximal hemostatic response requires both PAR receptors and the GpIb receptors.

Heterotrimeric G proteins

Over the past year, the thrust of work in the field of heterotrimeric G proteins has been primarily in the following areas: first, resolution of their three-dimensional structures by X-ray crystallography; second, elucidation of the effect of lipid modifications on the Galpha and Ggamma subunits; third, understanding the role of the Gbetagamma dimer in stimulation of a variety of effectors following receptor activation; and fourth, identification of the points of contact among the Galpha, Gbeta, and Ggamma subunits, and between these subunits and their cognate receptor or effector molecules.