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CB 1 cannabinoid receptor‐phosphorylated fourth intracellular loop structure‐function relationships
Author(s) -
Eldeeb Khalil,
Ganjiwale Anjali D.,
Chandrashekaran Indu R.,
Padgett Lea W.,
Burgess Jason P.,
Howlett Allyn C.,
Cowsik Sudha M.
Publication year - 2019
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.533
H-Index - 7
ISSN - 2475-8817
DOI - 10.1002/pep2.24104
Subject(s) - phosphorylation , intracellular , protein kinase c , protein kinase a , cyclic adenosine monophosphate , circular dichroism , microbiology and biotechnology , adenosine , chemistry , signal transduction , biochemistry , receptor , biology
A peptide comprising the juxtamembrane C‐terminal intracellular loop 4 (IL4) of the CB 1 cannabinoid receptor possesses three serine residues (Ser402, Ser411, and Ser415). We report the effect of Ser phosphorylation on the CB 1 IL4 peptide conformation and cellular signaling functions using nuclear magnetic resonance spectroscopy, circular dichroism (CD), G protein activation, and cyclic adenosine monophosphate (cAMP) production. Phosphorylation at Ser residues induced helical structure in different environments. Helical content varies in the order of IL4p‐Ser411 > IL4pSer415 > IL4 > IL4pSer402. The efficacy of phosphorylated IL4 peptides in activating Go and Gi3 ([ 35 S]GTPγS binding) and inhibiting cAMP accumulation in N18TG2 cells was correlated with helicity changes. Bradykinin treatment, which activates protein kinase C (PKC), augmented CB 1 ‐mediated inhibition of cAMP accumulation, and this was reversed by a PKC inhibitor. We conclude that phosphorylation‐dependent alterations of helicity of CB 1 IL4 peptides can augment G protein signaling.