Bradykinin regulates calpain and proinflammatory signaling through TRPM7-sensitive pathways in vascular smooth muscle cells

Abstract

Yogi A, Callera GE, Tostes R, Touyz RM. Bradykinin regulates calpain and proinflammatory signaling through TRPM7-sensitive pathways in vascular smooth muscle cells. Am J Physiol Regul Integr Comp Physiol 296: R201-R207, 2009. First published September 17, 2008 doi:10.1152/ajpregu.90602.2008.-Transient receptor potential melastatin-7 (TRPM7) channels have recently been identified to be regulated by vasoactive agents acting through G protein-coupled receptors in vascular smooth muscle cells (VSMC). However, downstream targets and functional responses remain unclear. We investigated the subcellular localization of TRPM7 in VSMCs and questioned the role of TRPM7 in proinflammatory signaling by bradykinin. VSMCs from Wistar-Kyoto rats were studied. Cell fractionation by sucrose gradient and differential centrifugation demonstrated that in bradykinin-stimulated cells, TRPM7 localized in fractions corresponding to caveolae. Immunofluorescence confocal microscopy revealed that TRPM7 distributes along the cell membrane, that it has a reticular-type intracellular distribution, and that it colocalizes with flotillin-2, a marker of lipid rafts. Bradykinin increased expression of calpain, a TRPM7 target, and stimulated its cytosol/membrane translocation, an effect blocked by 2-APB (TRPM7 inhibitor) and U-73122 (phospholipase C inhibitor), but not by chelerythrine (PKC inhibitor). Expression of proinflammatory mediators VCAM-1 and cyclooxygenase-2 (COX-2) was time-dependently increased by bradykinin. This effect was blocked by Hoe-140 (B 2 receptor blocker) and 2-APB. Our data demonstrate that in bradykinin-stimulated VSMCs: 1) TRPM7 is upregulated, 2) TRPM7 associates with cholesterol-rich microdomains, and 3) calpain and proinflammatory mediators VCAM-1 and COX2 are regulated, in part, via TRPM7-and phospholipase C-dependent pathways through B 2 receptors. These findings identify a novel signaling pathway for bradykinin, which involves TRPM7. Such phenomena may play a role in bradykinin/B 2 receptor-mediated inflammatory responses in vascular cells.

Identification of a Binding Motif in the S5 Helix That Confers Cholesterol Sensitivity to the TRPV1 Ion Channel

“…We speculate that the activity of TRPV1 could be regulated by expression of the Val/Val or Ile/Ile variants in cells with different cholesterol concentrations, or by transferring them between non-raft (low cholesterol) and raft (high cholesterol) microdomains within a given plasma membrane. For example, after exposure to bradykinin TRPM7 channels have been shown to relocalize from cholesterol-poor (non-raft) to cholesterol-rich (raft) domains (50). In the future, these variants may prove to display a physiologically important role in humans containing both variants of TRPV1 under conditions of hypercholesterolemia, for instance.…”

Molecular identification of ancient and modern mammalian magnesium transporters

“…Angiotensin II (59), aldosterone (77), bradykinin (9,104,177), epidermal growth factor (149), thrombin, (147), estrogen (48), metabolic acidosis/alkalosis (54, 82, 100), thiazide diuretics (101), the immunosuppressants tacrolimus (99) and cyclosporin A (69), and mechano-or osmo-induced stretch (4, 53, 102) have been implicated in alteration of TRPM7 and/or TRPM6 in a variety of cells. These changes may be mediated by covalent means, such as PLC-coupled receptors (77), or through controls at the transcript or protein level (49, 101,116,156).…”

TRPM7 in cerebral ischemia and potential target for drug development in stroke

“…The TRPM7 protein shown by immunofl uorescent labeling is strongly expressed at the plasma membrane in N1E-115 neuroblastoma cells [45] , and in vascular smooth muscle cells [46] . In N1E-115 neuroblastoma cells, HA-tagged TRPM7 antibodies were localized in membrane ruffl es [45] .…”