Isoforms of Kalirin, a Neuronal Dbl Family Member, Generated through Use of Different 5′- and 3′-Ends Along with an Internal Translational Initiation Site

doi:10.1074/jbc.M000676200

Isoforms of Kalirin, a Neuronal Dbl Family Member, Generated through Use of Different 5′- and 3′-Ends Along with an Internal Translational Initiation Site*

From the Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205

Abstract

Kalirin is a neuron-specific GDP/GTP exchange factor for Rho subfamily GTP-binding proteins. The major Kalirin transcripts in adult rat brain were identified. Most include a Sec14p-like putative lipid-binding motif followed by nine spectrin-like repeats and a Dbl homology/pleckstrin homology (DH-PH) domain. Kalirin proteins with four different NH₂ termini are generated through the use of five different 5′-ends; three of the proteins differ only at the extreme NH₂ terminus, and one is truncated because translation is initiated at a methionine in the 5th spectrin repeat. Four different 3′-ends yield Kalirin proteins with additional functional domains. Kalirin-7 (7-kilobase pair mRNA) terminates with a PDZ-binding motif, which in Kalirin-8 is replaced by an SH3 domain. Kalirin-9 contains another pair of DH-PH and SH3 domains. Kalirin-12 additionally encodes a putative Ser/Thr protein kinase. Antisera specific for different COOH termini established Kalirin-7 as the most abundant in cortex, with significant amounts of Kalirin-9 and Kalirin-12; Kalirin-7 was less prevalent in cerebellum and olfactory bulb. Kalirin proteins lacking the Sec14p-like domain and first four spectrin-like repeats were much less prevalent. Form-specific antisera demonstrated that different forms of Kalirin were localized to distinct subcellular regions of cultured neurons. Members of the family of Kalirin proteins may subserve different functions at these different locations.

Footnotes

↵* This work was supported by National Institutes of Health Grant DK-32948.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.
↵‡ Current address and to whom correspondence should be addressed: Dept. of Neuroscience, University of Connecticut Health Center, MC3401, 263 Farmington Ave., Farmington, CT 06030-3401. Tel.: 860-679-8894; Fax: 860-679-8766; E-mail: mains@nso.uchc.edu.
Published, JBC Papers in Press, April 20, 2000, DOI 10.1074/jbc.M000676200
Abbreviations:

GEFs

GDP/GTP exchange factors

DH

Dbl (deleted in B-cell lymphoma) homology

PAM

peptidylglycine α-amidating monooxygenase

pBS

pBluescript

P-CIP

PAM-COOH-terminal interactor protein

PH

pleckstrin homology

RACE

rapid amplification of cDNA ends

RT-PCR

reverse transcription-polymerase chain reaction

PAGE

polyacrylamide gel electrophoresis

SH3

src homology 3

iNOS

inducible nitric-oxide synthase

nt

nucleotides

kb

kilobase pair

bp

base pair

UTR

untranslated region

RACE

rapid amplification of cDNA ends
- Received January 29, 2000.
- Revision received March 29, 2000.
The American Society for Biochemistry and Molecular Biology, Inc.