Evidence that Rap1 carboxylmethylation is involved in regulated insulin secretion

M. Leiser, S. Efrat, N. Fleischer

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Protein carboxylmethylation is a reversible posttranslational modification that regulates protein function. We examined the carboxylmethylation of small GTP-binding proteins in a pancreatic β-cell line (βTC cells). In vitro assays showed that carboxylmethylation of a membrane 23-kDa protein was induced by guanine nucleotides, best demonstrated by the nonhydrolyzable GTP analog, guanosine 5'-(3-O-thio)triphosphate (GTPγS). GTPγS also induced translocation of this 23-kilodalton (kDa) protein from cytosol to particulate fractions. Immunoblotting with antiserum sc-65 raised against Rap1 identified the carboxyl-methylated 23-kDa protein as Rap1. 1) The 23-kDa carboxyl- methylated protein separated by two-dimensional electrophoresis overlapped with the 23-kDa protein detected by immunoblotting. 2) GTPγS, in the presence of cytosol, increased the amount of detectable membrane-associated Rap1. Studies in intact βTC cells demonstrated the carboxylmethylation of the 23-kDa protein in response to glucose and depolarizing concentrations of potassium, an effect that was abolished by the calcium channel inhibitor, D600. Similarly, N-acetyl-S-trans,trans-farnesyl-L-cysteine, an inhibitor of in vivo carboxylmethylation at COOH-terminal S-farnesylcysteine by methyltransferase, inhibited carboxylmethylation of the 23-kDa protein in intact cells and reduced insulin secretion in response to glucose and potassium. These data establish a correlation between insulin secretion and carboxylmethylation of a 23-kDa protein that comigrates with Rap1.

Original languageEnglish (US)
Pages (from-to)2521-2530
Number of pages10
JournalEndocrinology
Volume136
Issue number6
StatePublished - 1995

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Insulin
Proteins
Immunoblotting
Cytosol
Potassium
Gallopamil
Guanosine 5'-O-(3-Thiotriphosphate)
Glucose
Guanine Nucleotides
Membranes
Methyltransferases
Calcium Channels
Post Translational Protein Processing
Guanosine Triphosphate
GTP-Binding Proteins
Electrophoresis
Immune Sera
Cell Line

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Leiser, M., Efrat, S., & Fleischer, N. (1995). Evidence that Rap1 carboxylmethylation is involved in regulated insulin secretion. Endocrinology, 136(6), 2521-2530.

Evidence that Rap1 carboxylmethylation is involved in regulated insulin secretion. / Leiser, M.; Efrat, S.; Fleischer, N.

In: Endocrinology, Vol. 136, No. 6, 1995, p. 2521-2530.

Research output: Contribution to journalArticle

Leiser, M, Efrat, S & Fleischer, N 1995, 'Evidence that Rap1 carboxylmethylation is involved in regulated insulin secretion', Endocrinology, vol. 136, no. 6, pp. 2521-2530.
Leiser, M. ; Efrat, S. ; Fleischer, N. / Evidence that Rap1 carboxylmethylation is involved in regulated insulin secretion. In: Endocrinology. 1995 ; Vol. 136, No. 6. pp. 2521-2530.
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