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J. Biol. Chem., Vol. 281, Issue 35, 25250-25258, September 1, 2006

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Native TRPC7 Channel Activation by an Inositol Trisphosphate Receptor-dependent Mechanism^*

Guillermo Vazquez¹, Gary St. J. Bird, Yasuo Mori, and James W. Putney, Jr.

From the NIEHS, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709 and Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan

In DT40 B lymphocytes, Canonical Transient Receptor Potential 7 (TRPC7) functions as a diacylglycerol-activated non-selective cation channel. However, previous work indicated that the non-store-operated Ca²⁺ entry in this cell type depends upon inositol trisphosphate receptors (IP₃R). With the cell-attached configuration oleyl-acetyl-glycerol (OAG) induced single channel activity (75 pS) that was not observed in TRPC7^–/– cells but was rescued by expression of TRPC7 under conditions expected to produce relatively low levels of expression (^LowT7TRPC7^–/–). A DT40 cell line lacking IP₃R(IP₃R^–/– cells) showed no OAG-induced single channel activity, but this activity was rescued by transient expression of an IP₃R(^IP3RIP3R^–/–). Single channel properties in ^LowT7TRPC7^–/– or ^IP3RIP3R^–/– DT40 cells were indistinguishable from one another and from wild-type cells. Thus, TRPC7 forms, or is part of, the channel underlying endogenous diacylglycerol-activated currents in DT40 B lymphocytes, and this activity of native TRPC7 requires IP₃R. However, with conditions expected to produce greater expression levels, TRPC7 functioned independently of the presence of IP₃R. This finding may serve to resolve previously conflicting reports from expression studies of TRPC channels.

Received for publication, May 24, 2006 , and in revised form, June 29, 2006.

^* This work was supported in part by funds from the intramural program, NIEHS, National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: NIEHS, P. O. Box 12233, Research Triangle Park, NC 27709. E-mail: vazquez1{at}niehs.nih.gov.

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