Inositol 1,4,5-trisphosphate receptor down-regulation is activated directly by inositol 1,4,5-trisphosphate binding: Studies with binding- defective mutant receptors

Chang Cheng Zhu, Teiichi Furuichi, Katsuhiko Mikoshiba, Richard J.H. Wojcikiewicz

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

Activation of certain phosphoinositidase C-linked cell surface receptors is known to cause an acceleration of the proteolysis of inositol 1,4,5- trisphosphate (InsP3) receptors and, thus, lead to InsP3 receptor down- regulation. To gain insight into this process, we examined whether or not InsP3 receptor degradation is a direct consequence of InsP3 binding by analyzing the downregulation of exogenous wild-type and binding-defective mutant InsP3 receptors expressed in SH-SY5Y human neuroblastoma cells. Stimulation of these cells with carbachol showed that wild-type exogenous receptors could be down-regulated but that the binding-defective mutant exogenous receptors were not. Thus, InsP3 binding appears to mediate down- regulation. To validate this conclusion, a comprehensive analysis of the effects of the exogenous receptors was undertaken. This showed that exogenous receptors (i) are localized appropriately within the cell, (ii) enhance InsP3-induced Ca2+ release in permeabilized cells, presumably by increasing the number of InsP3-sensitive Ca2+ channels, (iii) have minimal effects on Ca2+ mobilization and InsP3 formation in intact cells, (iv) form heteromers with endogenous receptors, and (v) do not alter the down- regulation of endogenous receptors. In total, these data show that the introduction of exogenous receptors into SHSY5Y cells does not compromise intracellular signaling or the down-regulatory process. We can thus conclude that InsP3 binding directly activates InsP3 receptor degradation. Because InsP3 binding induces a conformational change in the InsP3 receptor, these data suggest that this change provides the signal for accelerated proteolysis.

Original languageEnglish (US)
Pages (from-to)3476-3484
Number of pages9
JournalJournal of Biological Chemistry
Volume274
Issue number6
DOIs
StatePublished - Feb 5 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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