A patient with multiple endocrine neoplasia type 1 (MEN1) has a gastrinoma. The hormone gastrin acts via which receptor mechanism?
- A Gs-coupled receptor activating adenylyl cyclase
- B Receptor tyrosine kinase with intrinsic kinase activity
- C Gq-coupled receptor activating phospholipase C ✓
- D Nuclear receptor binding DNA response elements
Correct answer: C. Gq-coupled receptor activating phospholipase C
Explanation
Gastrin receptors (CCK-B/gastrin receptors) are Gq-protein coupled receptors. Gq activates phospholipase C-beta, which cleaves PIP2 into DAG and IP3. IP3 releases Ca2+ from the endoplasmic reticulum, and DAG activates PKC, both promoting gastric acid secretion. Gs-cAMP mechanisms are used by secretin, VIP, and glucagon.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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