In Vivo Coupling of Insulin-like Growth Factor II/Mannose 6-Phosphate Receptor to Heteromeric G Proteins

doi:10.1074/jbc.270.49.29224

In Vivo Coupling of Insulin-like Growth Factor II/Mannose 6-Phosphate Receptor to Heteromeric G Proteins

DISTINCT ROLES OF CYTOPLASMIC DOMAINS AND SIGNAL SEQUESTRATION BY THE RECEPTOR (*)

From the (1)Shriners Hospitals for Crippled Children, Department of Anesthesia, Massachusetts General Hospital, Boston, Massachusetts 02114
(2)Cardiovascular Research Center, Massachusetts General Hospital, Departments of Medicine, Harvard Medical School, Charlestown, Massachusetts 02129
(3)Department of Stem Cell Regulation, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108, Japan

**To whom correspondence should be addressed. Tel.: 617-726-3902; Fax: 617-726-5806; nishimoto{at}helix.mgh.harvard.edu.

Abstract

We examined the signaling function of the IGF-II/mannose 6-phosphate receptor (IGF-IIR) by transfecting IGF-IIR cDNAs into COS cells, where adenylyl cyclase (AC) was inhibited by transfection of constitutively activated Gα cDNA (GαQ205L). In cells transfected with IGF-IIR cDNA, IGF-II decreased cAMP accumulation promoted by cholera toxin or forskolin. This effect of IGF-II was not observed in untransfected cells or in cells transfected with IGF-IIRs lacking Arg-Lys. Thus, IGF-IIR, through its cytoplasmic domain, mediates the G-linked action of IGF-II in living cells. We also found that IGF-IIR truncated with C-terminal 28 residues after Ser caused Gβ -dominant response of AC in response to IGF-II by activating G. Comparison with the Gα-dominant response of AC by intact IGF-IIR suggests that the C-terminal 28-residue region inactivates Gβ. This study not only provides further evidence that IGF-IIR has IGF-II-dependent signaling function to interact with heteromeric G proteins with distinct roles by different cytoplasmic domains, it also suggests that IGF-IIR can separate and sequestrate the Gα and Gβ signals following G activation.

Footnotes

↵^§ The first two authors contributed equally to this work.
↵^¶ Recipient of a fellowship from JSPS.
↵(*) This work was supported in part by Bristol-Myers Squibb. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

IGF-I and -II

insulin-like growth factors I and II, respectively

IGF-IR and IGF-IIR

the receptors for IGF-I and IGF-II, respectively

M6P

mannose 6-phosphate

AC

adenylyl cyclase

DMEM

Dulbecco's modified Eagle's medium

ΔCT41 or ΔCT28

mutant IGF-IIR lacking the C-terminal 41 residues after Arg or the 28 residues after Ser, respectively

Δ2410-2423

mutant IGF-IIR lacking Arg-Lys

Gα

α subunit of G

Gα

α subunit of transducin

CTX

cholera toxin

PTX

pertussis toxin

PH

pleckstrin homology.
- Received September 28, 1995.