Osmotic Stress Reduces Ca2+ Signals through Deformation of Caveolae.

Caveolae are membrane invaginations that can sequester various signaling proteins. Caveolae have been shown to provide mechanical strength to cells by flattening to accommodate increased volume when cells are subjected to hypo-osmotic stress. We have previously found that caveolin, the main structural component of caveolae, specifically binds Gαq and stabilizes its activation state resulting in an enhanced Ca(2+) signal upon activation. Here, we show that osmotic stress caused by decreasing the osmolarity in half reversibly changes the configuration of caveolae without releasing a significant portion of caveolin molecules. This change in configuration due to flattening leads to a loss in Cav1-Gαq association. This loss in Gαq/Cav1 association due to osmotic stress results in a significant reduction of Gαq/phospholipase Cß-mediated Ca(2+) signals. This reduced Ca(2+) response is also seen when caveolae are reduced by treatment with siRNA(Cav1) or by dissolving them by methyl-ß-cyclodextran. No change in Ca(2+) release with osmotic swelling can be seen when growth factor pathways are activated. Taken together, these results connect the mechanical deformation of caveolae to Gαq-mediated Ca(2+) signals.

Association between Psoriasis and MTHFR polymorphisms: a systematic review and meta-analysis.

Methylenetetrahydrofolate reductase (MTHFR) is key to the metabolism of folic acid, with loss of function mutations resulting in elevated homocysteine levels, a known risk factor for cardiovascular disease. Psoriasis patients may demonstrate hyperhomocysteinemia. To assess for the association between psoriasis and MTHFR C677T and A1298C polymorphisms. A systematic literature search was conducted in MEDLINE, Embase, Cochrane CENTRAL, and Web of Science. Case reports, case-control, cohort, and cross-sectional studies with full-text availability in English were considered. Meta-analysis was conducted with pooled ORs calculated via the random effects model (I2 > 50%). Of 917 records identified, 10 studies were selected for review of 1965 psoriasis patients and 2030 controls. Meta-analysis demonstrated that for MTHFR C677T, there were positive associations between psoriasis and the allele contrast model (C vs T, pooled OR = 1.69, 95% CI = 1.10-2.59), the additive model (CC vs TT, pooled OR = 2.44, 95% CI = 1.06-5.60), the dominant model (CC vs CT + TT, pooled OR = 1.77, 95% CI = 1.06-2.98), and the recessive model (CC + CT vs TT, pooled OR = 2.08, 95% CI = 1.05-4.13). For MTHFR A1298C, there were positive associations between psoriasis and the allele contrast model (A vs C, pooled OR = 3.57, 95% CI = 1.19-10.68), the dominant model (AA vs AC + CC, pooled OR = 4.44, 95% CI = 1.12-17.66), and the overdominant model (AC vs AA + CC, pooled OR = 0.26, 95% CI = 0.07-0.91). There may be a link between the C677T and A1298C polymorphisms with psoriasis diagnosis.