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The hop domain of the PAC1 receptor confers coupling to intracellular Ca 2+ elevation required for PACAP‐evoked catecholamine secretion
Author(s) -
Mustafa Tomris,
Walsh James,
Grimaldi Maurizio,
Eiden Lee
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.a982-b
Subject(s) - secretion , receptor , chemistry , extracellular , intracellular , medicine , endocrinology , cytosol , adenylate kinase , catecholamine , microbiology and biotechnology , biophysics , biology , biochemistry , enzyme
The molecular determinants for pituitary adenylate cyclase‐activating polypeptide (PACAP) evoked voltage‐gated Ca 2+ channel‐dependent catecholamine secretion from bovine adrenal chromaffin cells (BCCs) through its G‐protein coupled receptor have not been elucidated. We have found that BCCs express only one variant of the PAC1 receptor (bPAC1 hop ), and studied the structural requirements for its coupling to Ca 2+ following expression in PC12‐G cells, which secrete catecholamines in response to elevated potassium, but not PACAP. bPAC1 hop expression in PC12‐G cells confers high‐density PACAP binding, PACAP‐mediated Ca 2+ release from cytosolic stores, and sustained Ca 2+ influx which is blocked by the store‐operated Ca 2+ channel blocker 2‐aminoethoxydiphenyl borate (2‐APB; 10 μM). Removal of the hop domain from the third intracellular loop of the receptor abolished both Ca 2+ mobilization and influx without affecting receptor affinity or Gαs coupling. PACAP‐evoked norepinephrine secretion in bPAC1 hop − expressing PC12‐G cells was blocked both by 2‐APB and removal of extracellular Ca 2+ . These results demonstrate that the hop cassette confers PACAP‐dependent secretory competence to the PAC1 receptor via cell‐specific coupling of receptor activation to either store‐operated or voltage‐gated Ca 2+ channels.