Identification of a Novel Cysteine String Protein Variant and Expression of Cysteine String Proteins in Non-neuronal Cells

doi:10.1074/jbc.271.13.7320

Identification of a Novel Cysteine String Protein Variant and Expression of Cysteine String Proteins in Non-neuronal Cells (*)

From the Physiological Laboratory, University of Liverpool, Liverpool L69 3BX, United Kingdom

^¶To whom correspondence should be addressed:
Physiological Laboratory, University of Liverpool, Crown St., Liverpool L69 3BX, United Kingdom.
Tel.: 44-151-794-5305; Fax: 44-151-794-5337.

Abstract

Cysteine string proteins (Csps) are synaptic vesicle proteins thought to be involved in calcium-dependent neurotransmitter release at nerve endings. Here, we report the cloning of two Csp variants, termed Csp1 and Csp2, from bovine adrenal medullary chromaffin cells. The bovine Csp1 appears to be the homologue of rat brain Csp, sharing 95% identity at the amino acid level. The nucleotide sequence of csp2 is identical with that of csp1 except for a 72-base insert which introduces a stop codon into the coding sequence, which would be predicted to result in a truncated protein 3.3 kDa smaller than Csp1. Furthermore, polymerase chain reaction analysis detected homologues of Csp1 and Csp2 in rat kidney, liver, pancreas, spleen, lung, and adrenal gland. Expression of Csps in non-neuronal tissues was confirmed by Northern blotting and by immunoblotting with anti-Csp1 antiserum which also demonstrated expression of both full-length and truncated Csps in spleen. The widespread tissue distribution is inconsistent with a role for Csps as specific regulators of presynaptic calcium channels as previously proposed. We suggest that Csps may have a more general role in membrane traffic in non-neuronal as well as neuronal cells.

Footnotes

↵^§ Supported by a Wellcome Trust Prize Studentship.
↵* This work was supported in part by a grant from the Wellcome Trust. 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.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(™)/EMBL Data Bank with accession number(s) X92666 and X92667.
↵¹ The abbreviations used are:

Csp

cysteine string protein

PCR

polymerase chain reaction

SSPE

saline-sodium phosphate-EDTA buffer

Ni-NTA

nickel-nitrilotriacetic acid.
- Received December 18, 1995.
- Revision received January 9, 1996.