Evidence of calcium influx across the plasma membrane depends upon the initial rise of cytosolic calcium with activation of IP3 in rat enterocytes by heat-stable enterotoxin of Vibrio cholerae non-O1

Abstract

In response to heat-stable enterotoxin of Vibrio cholerae non-O1, the initial rise of cytosolic 2 entry to the cell as assessed by Mn 2 quenching of fura-2 fluorescence which suggested that calcium influx across the plasma membrane depends upon initial rise of this bivalent cation that maintained the sustained phase of [Ca 2 ]i response. Addition of toxin to the fura-2-loaded cells, preincubated with lanthanum chloride, resulted in reduction of [Ca 2 ]i level with a short duration of irregular sustained phase further suggesting that the influx of Ca 2 across the plasma membrane might be through the calcium channel. ß

Culture supernatants from V. cholerae O1 ElTor strains isolated from different geographic areas induce cell vacuolation and cytotoxicity

“…2 The recently described cholix toxin, secreted by non-O1 strains, possesses ADP-ribose transferase activity against ribosomal eukaryotic elongation factor. 3 V. cholerae ElTor haemolysin (HlyA) is another important toxin secreted by most V. cholerae O1 and non-O1 strains.…”

Mechanisms of somatostatin-induced paradoxical increase in insulin secretion in the presence of arginine vasopressin in clonal [beta]-cell HIT-T15

“…Previously, we demonstrated that in the presence of AVP, which signals via Gq, SRIF increased [Ca 2 *} leading to insulin secretion in HIT-T15 cells [21,22]. Our findings suggested that the mechanism by which SRIF signals be through Gi/Go, and involve the phospholipase C pathway and mainly Ca 2 * release from the endoplasmic reticulum.…”

“…Studies in COS-1 cells provide further support for the Py dimer mediation of the cross-talk between the Gq-and Gi-coupled receptors [23]. Enhancement of Gq-dependent signals by Gi-coupled receptors in COS-7 cells requires an activated PLC-p and is mediated by the Py dimer [21]. In addition, activation of Gi/Go-coupled receptors has been shown to enhance the inositol phosphate signals generated by Gq-coupled receptors [28,29].…”

“…Cross-talks between Gq and Gi/Go have been described in human neuroblastoma SH-SY5Y and COS cells [21][22][23]. In HIT-T15 cells, AVP binds V 1b receptors [24], which couples to Gq, thus activating PLC-p through the aq subunit with subsequent hydrolysis of Ptdlns(4,5)P 2 to lns(1,4,5)P 3 and diacylglycerol (DAG) [25].…”

Somatostatin Increases Phospholipase D Activity and Phosphatidylinositol 4,5-bisphosphate Synthesis in Clonal β Cells HIT-T15

“…Measurement of inositol phosphates followed modified procedures from a published report (Hoque et al, 2001). Cells were labeled with 20 Ci/ml of myo-[2-3 H]inositol at 37°C for 90 min, by which time the incorporation of 3 H into inositol lipids had reached a plateau (Hoque et al, 2001).…”