Lim CH, Schoonderwoerd K, Kleijer WJ, de Jonge HR, Tilly BC. Regulation of the cell swelling-activated chloride conductance by cholesterol-rich membrane domains.
Acta Physiol (Oxf) 2006;
187:295-303. [PMID:
16734766 DOI:
10.1111/j.1748-1716.2006.01534.x]
[Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
AIM
The role of high cholesterol-containing microdomains in the signal transduction cascade leading to the activation of volume-regulated anion channels (VRACs) was studied.
METHODS
Osmotic cell swelling-induced efflux of 125I- was determined in human epithelial Intestine 407 cells and in skin fibroblasts obtained from healthy controls or Niemann-Pick type C (NPC) patients. Cellular cholesterol content was modulated by pre-incubation with 2-hydroxypropyl-beta-cyclodextrin in the presence of acceptor lipid vesicles.
RESULTS
Osmotic cell swelling of human Intestine 407 cells leads to the rapid activation of a compensatory anion conductance. Treatment of the cells with cyclodextrin enhanced the response to submaximal hypotonic stimulation by approx. twofold, but did not further increase the efflux elicited by a saturating stimulus. In contrast, the volume-sensitive anion efflux was markedly inhibited when cholesterol-loaded cyclodextrin was used. Potentiation of the response by cholesterol depletion was maintained in caveolin-1 deficient Caco-2 colonocytes as well as in sphingomyelinase-treated Intestine 407 cells, indicating that cholesterol-rich microdomains are not crucially involved. However, treatment of the cells with progesterone, an inhibitor of NPC1-dependent endosomal cholesterol trafficking, not only markedly reduced the hypotonicity-provoked anion efflux, but also prevented its potentiation by cyclodextrin. In addition, the volume-sensitive anion efflux from human NPC skin fibroblasts was significantly smaller when compared with control fibroblasts.
CONCLUSIONS
The results support a model of regulatory volume decrease involving recruitment of volume-sensitive anion channels from intracellular compartments to the plasma membrane.
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