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Regulation of Caveolin‐2 Phosphorylation at Serines 23 and 36
Author(s) -
Sowa Grzegorz,
Sessa William
Publication year - 2007
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.21.6.a1424-b
Subject(s) - phosphorylation , serine , caveolae , lipid raft , microbiology and biotechnology , cell fractionation , caveolin 1 , phosphoserine , protein phosphorylation , chemistry , biology , biochemistry , signal transduction , membrane , protein kinase a
Previously, we have shown that caveolin‐2 (Cav‐2) is phosphorylated under basal conditions at N‐terminal serine residues 23 and 36 and that phosphorylation of Cav‐2 plays a positive role in caveolae assembly in a reconstituted system, LNCaP cells expressing recombinant caveolins. In the present study, we show that serine phosphorylation of Cav‐2 also occurs in endothelial cells (ECs) and is regulated by Cav‐1 and subcellular location. More specifically, using adenoviral expression and phospho‐specific antibodies to Cav‐2, we demonstrate that co‐expression of Cav‐1 increases by ca. 3‐fold phosphorylation of Cav‐2 at serine residue 23, and decreases by ca. 2‐fold phosphorylation of serine 36 in cells expressing Cav‐1 and ‐2, relative to cells expressing Cav‐2 alone. Consistent with the latter, the ratio of serine 23 phosphorylated to total Cav‐2 protein in human ECs is 7‐fold higher than in cells expressing Cav‐2 alone, while the respective ratio of serine 36 phosphorylation is 1.5‐fold lower. Subcellular fractionation techniques, separating lipid rafts/caveolae, have determined that serine 23 phosphorylation of Cav‐2 preferably occurs in lipid rafts/caveolae. Conversely, serine 36 phosphorylation takes place in non‐lipid raft/caveolar compartments. Our subcellular fractionation data are consistent with fluorescence microscopic studies on cells co‐expressing Cav‐1 and ‐2, which have shown that vast majority of serine 23‐phosphorylated Cav‐2 is located to plasma membrane, while serine 36 phosphorylated Cav‐2 to perinuclear region. In summary, serine phosphorylation of Cav‐2 is a regulated process, largely dependent on Cav‐1‐driven translocation of Cav‐2 from detergent soluble intracellular compartments to detergent insoluble plasma membrane associated lipid rafts and caveolae.