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Expression and localization of adenylyl cyclases and G protein‐coupled receptors in guinea pig ileum caveolae and lipid rafts
Author(s) -
Reece Richard,
Liu Xiaoqiu,
Sun Shu Q,
Ehlert Frederick J,
Ostrom Rennolds S
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.a792-a
Subject(s) - caveolae , adenylyl cyclase , receptor , lipid raft , caveolin , gene isoform , biology , g protein , microbiology and biotechnology , gs alpha subunit , endocrinology , chemistry , medicine , biochemistry , signal transduction , gene
We examined the expression and localization of adenylyl cyclase (AC) isoforms and G protein‐coupled receptors in guinea pig ileum longitudinal smooth muscle (SM). Using non‐detergent cell fractionation and sucrose gradient centrifugation, we isolated caveolae/lipid rafts from ileal SM from Hartley guinea pigs. Buoyant fractions expressed both caveolin‐1 and caveolin‐2 but excluded α‐SM actin. Immunoblotting for AC isoforms demonstrated that ileal smooth muscle express AC3, AC5/6 and AC8. Each of these AC isoforms was detected exclusively in buoyant, caveolin‐rich fractions, consistent with findings from other cells and tissues. β 1 ‐adrenergic receptor (βAR) immunoreactivity was detected in both the buoyant and heavy fractions but prostanoid EP 2 receptors were detected only in heavy fractions. Overexpression of AC6 led to prominent AC5/6 immunoreactivity in buoyant fractions and enhanced forskolin‐ and isoproterenol‐induced cAMP accumulation but did not effect PGE 2 ‐stimulated responses. AC6 overexpression in ileum altered histamine‐induced contractions, reducing the maximal percent contraction relative to KCl without altering histamine potency. Thus, ileal SM expresses predominantly caveolar/lipid raft localized isoforms of AC that are highly co‐localized with and functionally coupled to βAR. Prostanoid EP 2 receptors do not regulate the activity of these raft‐localized AC isoforms. Overexpression of AC6 in ileal SM appears to selectively enhance β‐adrenergic receptors responses. Supported by NIH grant HL079166.