
Eva Degerman
Professor

Identification of the phosphorylation site in vitro for cAMP-dependent protein kinase on the rat adipocyte cGMP-inhibited cAMP phosphodiesterase
Author
Summary, in English
Rat adipocyte cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) appears to be dually regulated in intact cells by serine phosphorylations induced by isoprenaline and insulin, respectively (Degerman, E., Smith, C. J., Tornqvist, H., Vasta, V., Belfrage, P., and Manganiello, V. C. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 533-537; Smith, C. J., Vasta, V., Degerman, E., Belfrage, P., and Manganiello, V. C. (1991) J. Biol. Chem. 266, 13385-13390). Since cAMP-dependent protein kinase (cAMP-PK) catalyzes the beta-adrenergic effects, the site in the isolated cGI-PDE phosphorylated by this kinase was explored. A peptide, LRRSSGASGLLTSEHHSR (P18), corresponding to the amino acid sequence Leu423-Arg440 in the putative regulatory domain of the rat adipocyte cGI-PDE was synthesized. It contains a consensus substrate sequence -RRXS- for cAMP-PK within two tryptic cleavage sites and was readily phosphorylated by cAMP-PK. Two phosphopeptides, identified as RS-[32P]SGASGLLTSEHHSR and S-[32P]SGASGLLTSEHHSR, were obtained after stoichiometric phosphorylation and trypsinization of the peptide. These two peptides and the two main tryptic phosphopeptides obtained from immunoisolated [32P]cGI-PDE phosphorylated with cAMP-PK in a solubilized crude adipocyte membrane fraction were immuno-precipitated by an affinity-purified polyclonal antibody raised against P18 and exhibited the same chromatographic and electrophoretic profiles in three different separation systems. Similar radiosequencing profiles indicated that the second most N-terminal serine, corresponding to Ser-427 in the intact cGI-PDE, was phosphorylated by cAMP-PK in both P18 and authentic cGI-PDE. It is concluded that serine 427 is the target for cAMP-PK phosphorylation of the rat adipocyte cGI-PDE in vitro.
Department/s
- Biotechnology
- Insulin Signal Transduction
Publishing year
1994
Language
English
Pages
11962-11966
Publication/Series
Journal of Biological Chemistry
Volume
269
Issue
16
Document type
Journal article
Publisher
ASBMB
Topic
- Endocrinology and Diabetes
Status
Published
Research group
- Insulin Signal Transduction
ISBN/ISSN/Other
- ISSN: 1083-351X