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Mechanism of homocysteine‐induced modulation of GPCRs
Author(s) -
Vacek Thomas Paul,
Sen Utpal,
Tyagi Neetu,
Moshal Karni Singh,
Passmore John,
Kumar Munish,
Steed Mesia,
Tyagi Suresh
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1155.20
Subject(s) - g protein coupled receptor , phosphorylation , beta adrenergic receptor kinase , chemistry , proto oncogene tyrosine protein kinase src , receptor , microbiology and biotechnology , signal transduction , g protein coupled receptor kinase , g protein , intracellular , agonist , biochemistry , pharmacology , biology
G protein coupled receptors (GPCRs) are known to modulate intracellular effectors involved in cardiac function. We recently reported (Hcy)‐induced ERK phosphorylation was suppressed by pertussis toxin (PTX), which suggests the involvement of G protein‐coupled receptors (GPCRs) in initiating signal transduction. An activated GPCR undergoes down‐regulation via a known mechanism involving GRK2, β‐arrestin1 and c‐SRC. Dephosphorylation of GRK2 at Ser670, of β‐arrestin1 at Ser412, and of c‐SRC at Tyr529 sites leads to an increase in the respective activities. We hypothesize that Hcy treatment leads to an increase in the activities of the GPCR proteins, causing sequestration and degradation of GPCRs via endocytosis. Microvascular endothelial cells (MVEC) were treated with varying doses of Hcy for 60 minutes. Expression of phospho‐ERK1, phospho‐GRK2, phospho‐β‐arrestin1 and phospho‐c‐SRC was determined using Western blot, standardized to ERK1, GRK2, β‐arrestin1, c‐SRC, and β‐actin. A standard treatment of Hcy (100μM) was selected for 0,15,30,45,60 and 120 minutes. Confocal analysis of phospho‐forms of ERK1, GRK2, β‐arrestin1, and c‐SRC was performed. Hcy was shown to decrease the expression of the phosphorylated forms of GRK2, β‐arrestin1, c‐SRC, thereby enhancing their activities. The results suggest that Hcy acts as an agonist to activate GPCRs, followed by their sequestration and degradation.