Phosphorylation and Activation of the Plasma Membrane Na+/H+ Exchanger (NHE1) during Osmotic Cell Shrinkage

The Na+/H+ Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na+/H+ exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na+/H+ exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na+ transport capacity without affecting transport affinity (Km = 44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ 32P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na+ transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events

Sulfhydryl Modification Induces Calcium Entry through IP3-Sensitive Store-Operated Pathway in Activation-Dependent Human Neutrophils

As the first line of host defense, neutrophils are stimulated by pro-inflammatory cytokines from resting state, facilitating the execution of immunomodulatory functions in activation state. Sulfhydryl modification has a regulatory role in a wide variety of physiological functions through mediation of signaling transductions in various cell types. Recent research suggested that two kinds of sulfhydryl modification, S-nitrosylation by exogenous nitric oxide (NO) and alkylation by N-ethylmaleimide (NEM), could induce calcium entry through a non-store-operated pathway in resting rat neutrophils and DDT1MF-2 cells, while in active human neutrophils a different process has been observed by us. In the present work, data showed that NEM induced a sharp rising of cytosolic calcium concentration ([Ca2+]c) without external calcium, followed by a second [Ca2+]c increase with readdition of external calcium in phorbol 12-myristate 13-acetate (PMA)-activated human neutrophils. Meanwhile, addition of external calcium did not cause [Ca2+]c change of Ca2+-free PMA-activated neutrophils before application of NEM. These data indicated that NEM could induce believable store-operated calcium entry (SOCE) in PMA-activated neutrophils. Besides, we found that sodium nitroprusside (SNP), a donor of exogenous NO, resulted in believable SOCE in PMA-activated human neutrophils via S-nitrosylation modification. In contrast, NEM and SNP have no effect on [Ca2+]c of resting neutrophils which were performed in suspension. Furthermore, 2-Aminoethoxydiphenyl borate, a reliable blocker of SOCE and an inhibitor of inositol 1,4,5-trisphosphate (IP3) receptor, evidently abolished SNP and NEM-induced calcium entry at 75 µM, while preventing calcium release in a concentration-dependent manner. Considered together, these results demonstrated that NEM and SNP induced calcium entry through an IP3-sensitive store-operated pathway of human neutrophils via sulfhydryl modification in a PMA-induced activation-dependent manner

Phenotypic characterisation of regulatory T cells in dogs reveals signature transcripts conserved in humans and mice

Regulatory T cells (Tregs) are a double-edged regulator of the immune system. Aberrations of Tregs correlate with pathogenesis of inflammatory, autoimmune and neoplastic disorders. Phenotypically and functionally distinct subsets of Tregs have been identified in humans and mice on the basis of their extensive portfolios of monoclonal antibodies (mAb) against Treg surface antigens. As an important veterinary species, dogs are increasingly recognised as an excellent model for many human diseases. However, insightful study of canine Tregs has been restrained by the limited availability of mAb. We therefore set out to characterise CD4+CD25high T cells isolated ex vivo from healthy dogs and showed that they possess a regulatory phenotype, function, and transcriptomic signature that resembles those of human and murine Tregs. By launching a cross-species comparison, we unveiled a conserved transcriptomic signature of Tregs and identified that transcript hip1 may have implications in Treg function

Heat shock proteins in porcine ovary: synthesis, accumulation and regulation by stress and hormones

The present studies aimed to understand the interrelationships between stress, hormones and heat shock proteins (HSPs) in the ovary. We examined (1) whether HSP70.2, HSP72 and HSP105/110 can be produced and accumulated in porcine ovarian tissue, (2) whether these HSPs could be indicators of stress, i.e. whether two kinds of stress (high temperatures and malnutrition/serum deprivation) can affect them, and (3) whether some hormonal regulators of ovarian functions (insulin-like growth factor (IGF)-I, leptin and follicle-stimulating hormone (FSH)) can affect these HSPs and response of ovaries to HSP-related stress. We analysed the expression of HSP70.2, HSP72 and HSP105/110 mRNA (by using real-time reverse transcriptase polymerase chain reaction) in porcine ovarian granulosa cells, as well as the accumulation of HSP70 protein (by using sodium dodecyl sulphate polyacrylamide gel electrophoresis–Western) in either whole ovarian follicles and granulose cells cultured at normal (37.5°C) or high (41.5°C) temperature, with and without serum and with and without IGF-I, leptin and FSH. Expression of mRNA for HSP70.2, HSP72 and HSP105/110 in ovarian granulosa cells and accumulation of HSP70 protein in whole ovarian follicles and granulosa cells were demonstrated. In all the groups, addition of either IGF-I, leptin and FSH reduced the expression of HSP70.2, HSP72 and HSP105/110 mRNA. Both high temperature, serum deprivation and their combination resulted in increase in mRNAs for all three analysed HSPs. Additions of either IGF-I, leptin and FSH prevented the stimulatory effect of both high temperature and serum deprivation on the transcription of HSP70.2, HSP72 and HSP105/110. In contrast, high temperature reduced accumulation of peptide HSP70 in both ovarian follicles and granulosa cell. Serum deprivation promoted accumulation of HSP70 in granulosa cells, but not in ovarian follicles. Addition of IGF-I, leptin and FSH was able to alter accumulation of HSP70 in both follicles and granulosa cells. The present observations suggest (1) that HSPs can be synthesised in ovarian follicular granulosa cells; (2) that hormones (IGF-I, leptin and FSH) can inhibit, whilst stressors (both high temperature and malnutrition/serum deprivation) can stimulate transcription of HSP70.2, HSP72 and HSP105/110 genes, whilst heat stress, but not malnutrition, can promote depletion of HSP70 in ovarian cells, and (3) that hormones (IGF-I, leptin and FSH) can prevent stress-related changes in HSPs. The application of HSPs as indicators and mediators of stress and hormones on ovarian functions, as well as use of hormones and HSPs as anti-stressor molecules, are discussed