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A genome-wide association study (GWAS) is conducted to understand the association of three common single-nucleotide polymorphisms (SNPs) with mean platelet volume (MVP). The results have helped in understanding the platelet activation and function of MVP, which increased in myocardial and cerebral infarction and is strong predictor for postevent morbidity and mortality.

Abstract Background Gastric inhibitory polypeptide (GIP) is postulated to be involved in type 2 diabetes mellitus and obesity. It exerts its function through its receptor, GIPR. We genotyped three GIPR SNPs (rs8111428, rs2302382 and rs1800437) in German families with at least one obese index patient, two case-control studies and two cross-sectional population-based studies. Methods Genotyping was performed by MALDI-TOF, ARMS-PCR and RFLP. The family-study: 761 German families with at least one extremely obese child or adolescent (n = 1,041) and both parents (n = 1,522). Case-control study: (a) German obese children (n = 333) and (b) obese adults (n = 987) in comparison to 588 adult lean controls. The two cross-sectional population-based studies: KORA (n = 8,269) and SHIP (n = 4,310). Results We detected over-transmission of the A-allele of rs2302382 in the German families (pTDT-Test = 0.0089). In the combined case-control sample, we estimated an odd ratio of 1.54 (95%CI 1.09;2.19, pCA-Test = 0.014) for homozygotes of the rs2302382 A-allele compared to individuals with no A-allele. A similar trend was found in KORA where the rs2302382 A-allele led to an increase of 0.12 BMI units (p = 0.136). In SHIP, however, the A-allele of rs2302382 was estimated to contribute an average decrease of 0.27 BMI units (p-value = 0.031). Conclusion Our data suggest a potential relevance of GIPR variants for obesity. However, additional studies are warranted in light of the conflicting results obtained in one of the two population-based studies.

The activity state of cofilin, which controls actin dynamics, is driven by a phosphorylation–dephosphorylation cycle. Phosphorylation of cofilin by LIM-kinases results in its inactivation, a process supported by 14-3-3ζ and reversed by dephosphorylation by slingshot phosphatases. Here we report on a novel cellular function for the phosphorylation–dephosphorylation cycle of cofilin. We demonstrate that muscarinic receptor-mediated stimulation of phospholipase D1 (PLD1) is controlled by LIM-kinase, slingshot phosphatase as well as 14-3-3ζ, and requires phosphorylatable cofilin. Cofilin directly and specifically interacts with PLD1 and upon phosphorylation by LIM-kinase1, stimulates PLD1 activity, an effect mimicked by phosphorylation-mimic cofilin mutants. The interaction of cofilin with PLD1 is under receptor control and encompasses a PLD1-specific fragment (aa 585–712). Expression of this fragment suppresses receptor-induced cofilin–PLD1 interaction as well as PLD stimulation and actin stress fiber formation. These data indicate that till now designated inactive phospho-cofilin exhibits an active cellular function, and suggest that phospho-cofilin by its stimulatory effect on PLD1 may control a large variety of cellular functions. [ABSTRACT FROM AUTHOR]

Dehydroepiandrosterone (DHEA) is the main adrenal androgen, which mostly exists in a sulfated version (DHEAS). Both DHEA and DHEAS are metabolic intermediates in the biosynthesis of the male sex hormone testosterone. In men, testosterone is involved in the regulation of fertility, libido, and muscle mass and is valuable for the assessment of gonadal, adrenal, and pituitary function and for the diagnosis of hypogonadism. The objective of the present study was to calculate age-specific reference ranges for serum DHEAS and serum testosterone using 1) linear regression and the mean +/- 1.96 standard deviation concept and 2) quantile regression. From the cross-sectional Study of Health in Pomerania a total of 1078 men aged 20-79 years were included in the analyses. Serum DHEAS and testosterone levels were quantified using IMMULITE 2500 immunoassays. Linear and quantile regression were performed to calculate age-specific reference ranges. Both statistical methods generated different results: The reference ranges based on linear regression identified 17 men (1.6%) with DHEAS levels and 45 men (4.2%) with serum testosterone levels outside the reference range. Using quantile regression, 54 men (5.0%) and 50 men (4.6%) with serum DHEAS and testosterone levels outside the range were detected, respectively. The present study established age-specific reference ranges for serum DHEAS and testosterone levels for men. Quantile regression should be preferred to calculate reference ranges; a better concordance with original data is possible because no distribution assumption is required and the robustness against outliers is given.

Receptor tyrosine kinase regulation of phospholipase C-epsilon (PLC-epsilon), which is under the control of Ras-like and Rho GTPases, was studied with HEK-293 cells endogenously expressing PLC-coupled epidermal growth factor (EGF) receptors. PLC and Ca(2+) signaling by the EGF receptor, which activated both PLC-gamma1 and PLC-epsilon, was specifically suppressed by inactivation of Ras-related GTPases with clostridial toxins and expression of dominant-negative Rap2B. EGF induced rapid and sustained GTP loading of Rap2B, binding of Rap2B to PLC-epsilon, and Rap2B-dependent translocation of PLC-epsilon to the plasma membrane. GTP loading of Rap2B by EGF was inhibited by chelation of intracellular Ca(2+) and expression of lipase-inactive PLC-gamma1 but not of PLC-epsilon. Expression of RasGRP3, a Ca(2+)/diacylglycerol-regulated guanine nucleotide exchange factor for Ras-like GTPases, but not expression of various other exchange factors enhanced GTP loading of Rap2B and PLC/Ca(2+) signaling by the EGF receptor. EGF induced tyrosine phosphorylation of RasGRP3, but not RasGRP1, apparently caused by c-Src; inhibition of c-Src interfered with EGF-induced Rap2B activation and PLC stimulation. Collectively, these data suggest that the EGF receptor triggers activation of Rap2B via PLC-gamma1 activation and tyrosine phosphorylation of RasGRP3 by c-Src, finally resulting in stimulation of PLC-epsilon.

The aim of this study was the characterization of the human Gbeta4 subunit of heterotrimeric G proteins. Human Gbeta4 is widely expressed. Its gene is located on chromosome 3 with a genomic structure indistinguishable from that of the genes of Gbeta1 to Gbeta3, but entirely different from Gbeta5. In vitro translation co-precipitation analyses revealed that Gbeta4 can form stable dimers with Ggamma1, Ggamma2, Ggamma3, Ggamma4, Ggamma5, Ggamma7, Ggamma10, Ggamma11, Ggamma12, and Ggamma13, dimers which were also able to stimulate phospholipase beta2.

The T-allele of a polymorphism (C825T) in the gene for the G-protein beta 3 subunit (GNB3) is associated with cardiovascular and metabolic disorders, distinct cellular features and altered drug responses. The molecular mechanisms that give rise to this complex phenotype have been linked to the occurrence of G beta 3s, a splice variant of GNB3. G beta 3s is predominantly expressed in cells with the 825T-allele. In the present study we describe the identification and characterization of an additional G beta 3 splice variant referred to as G beta 3s2. Its mRNA is expressed in heart, blood cells and tumour tissue, and its expression is also tightly associated with the GNB3 825T-allele. G beta 3s2 is generated by alternative splicing using non-canonical splice sites. G beta subunits belong to the family of propeller proteins and consist of seven regular propeller blades. Transcripts for G beta 3s2 are lacking 129 bp of the coding sequence of the wild-type G beta 3 protein. Thus the predicted structure consists of only six propeller blades, which resembles the structure of G beta 3s. Co-immunoprecipitation analyses indicated that G beta 3s2 dimerizes with different G gamma subunits, e.g. G gamma 5, G gamma 8(C) and G gamma 12. In Sf9 insect cells, expression of G beta 3s2 together with G gamma 12 enhances receptor-stimulated activation of G alpha(i2). Expression of G beta 3s2 in mammalian cells activated the mitogen-activated protein kinase cascade. Together, these results suggest that G beta 3s2 is a biologically active G beta variant which may play a role in the manifestation of the complex phenotype associated with the 825T-allele.

Somatostatin (SST) and somatostatin receptors (SSTR) are widely distributed in lymphoid tissues. Here, we report on the stimulatory effects of SST in Epstein-Barr virus-immortalized B lymphoblasts. By RT-PCR, we demonstrated the exclusive expression of the somatostatin receptor isoform 2A (SSTR2A) in B lymphoblasts. Addition of SST rapidly increased the cytosolic free calcium concentration [Ca(2+)](i) maximally by about 200 nM, with an EC(50) of 1.3 nM, and stimulated the formation of inositol phosphates. Furthermore, SST increased binding of guanosine 5'-O-(3-thiotriphosphate) by 50% above basal. These effects were partly inhibited by pertussis toxin (PTX), which indicates the involvement of PTX-sensitive G proteins. We provide further evidence that Galpha(16,) a PTX-insensitive G protein confined to lymphohematopoietic cells, is involved in the otherwise unusual coupling of SSTR2A to phospholipase C activation. In addition, SST activated extracellular regulated kinases and induced a 3.5-fold stimulation of DNA synthesis and a 4.4-fold stimulation of B lymphoblast proliferation, which was accompanied by an enhanced immunoglobulin formation. Thus SST exerts a growth factor-like activity on human B lymphoblasts.