Signaling Inositol Polyphosphate-5-phosphatase
CHARACTERIZATION OF ACTIVITY AND EFFECT OF GRB2 ASSOCIATION*
- Anne Bennett Jefferson‡¶,
- Vorachart Auethavekiat‡,
- David A. Pot,
- Lewis T. Williams and
- Philip W. Majerus‡∥
- From the ‡ Division of Hematology-Oncology, Washington University School of Medicine, Box 8125, St. Louis, Missouri 63110 and Chiron Corporation, Emeryville, California 94608
- ∥ To whom reprint requests should be sent. Tel.: 314-362-8801; Fax: 314-362-8826.
Abstract
An inositol polyphosphate-5-phosphatase (SIP-110) that binds the SH3 domains of the adaptor protein GRB2 was produced in Sf9 cells and characterized. SIP-110 binds to GRB2 in vitro with a stoichiometry of 1 mol of GRB2/0.7 mol of SIP-110. GRB2 binding does not affect enzyme activity implying that GRB2 serves mainly to localize SIP-110 within cells. SIP-110 hydrolyses inositol (Ins)(1,3,4,5)P4 to Ins(1,3,4)P3. The enzyme does not hydrolyze Ins(1,4,5)P3 that is a substrate for previously described 5-phosphatases nor does it hydrolyze phosphatidylinositol (PtdIns)(4,5)P2. SIP-110 also hydrolyzed PtdIns(3,4,5)P3 to PtdIns(3,4)P2 as did recombinant forms of two other 5-phosphatases designated as inositol polyphosphate-5- phosphatase II, and OCRL (the protein that is mutated in oculocerebrorenal syndrome). The inositol polyphosphate-5-phosphatase enzyme family now is represented by at least 9 distinct genes and includes enzymes that fall into 4 subfamilies based on their activities toward various 5-phosphatase substrates.
Footnotes
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↵* This work was supported by Grants HL14147 (Specialized Center for Research in Thrombosis) and HL16634 and HL32898 from the National Institutes of Health and Chiron Corp. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- PtdIns
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phosphatidylinositol
- GST
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glutathione S-transferase
- HPLC
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high performance liquid chromatography
- IP
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inositol phosphate
- OCRL
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oculocerebrorenal syndrome.
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- Received November 25, 1996.
- © 1997 by The American Society for Biochemistry and Molecular Biology, Inc.
