WBR0444

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Physiology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A researcher, studying the pathways that anti-diuretic hormone (ADH) undergoes before hormonal effect takes place, observes the signalling pathwasy of ADH V2 following release from the supraoptic nuclei in the posterior hypothalamus. Which of the following signaling pathways is utilized by ADH V2 receptors to achieve insertion of aquaporin-2 water channels in the collecting tubules of the kidney?]]
Answer A	AnswerA::G-coupled receptor pathway that eventually activates protein kinase A
Answer A Explanation	AnswerAExp::The G-coupled receptor pathway, which that eventually activates protein kinase A, is the signaling pathway of ADH V2.
Answer B	AnswerB::The receptor or intrinsic tyrosine kinase signaling pathway that eventually activates an adapter protein
Answer B Explanation	AnswerBExp::This pathway is utilized by insulin and other growth factors, but not ADH.
Answer C	AnswerC::G-coupled receptor pathway that eventually activates protein kinase C
Answer C Explanation	AnswerCExp::This pathway is utilized by ADH V1.
Answer D	AnswerD::G-coupled receptor pathway that eventually inhibits the activity of adenylyl cyclase
Answer D Explanation	AnswerDExp::Gi-coupled receptor pathway inactivates adenylyl cyclase. On the contrary, ADH V2 receptor activate adenylyl cyclase by acting on the Gs-coupled receptors.
Answer E	AnswerE::G-coupled receptor pathway that eventually leads to the formation of inositol triphosphate
Answer E Explanation	AnswerEExp::This pathway is utilized by ADH V1.
Right Answer	RightAnswer::A
Explanation	[[Explanation::There are several signaling pathways of the endocrine hormones. The signaling pathway utilized by ADH V2 is different that used by ADH V1. ADH V2 receptor activates the Gs-coupled receptor pathway, which activates adenylyl cyclase. This catalyzes the conversion of ATP to cyclic AMP (cAMP), activating protein kinase A. ADH V1 utilizes the Gq-coupled receptor pathway, activating phospholipase C, which leads to the formation of inositol triphosphate (IP3) and diacyl glycerol (DAG), as well as the activation of protein kinase C. Educational Objective: ADH V1 utilizes the Gq-coupled receptor pathway, activating phospholipase C, which leads to the formation of inositol triphosphate (IP3) and diacyl glycerol (DAG), as well as the activation of protein kinase C. References: First Aid 2014 page 311]]
Approved	Approved::Yes
Keyword	WBRKeyword::signaling, WBRKeyword::pathway, WBRKeyword::G couple, WBRKeyword::receptor, WBRKeyword::enzymes, WBRKeyword::kinase A, WBRKeyword::antidiuretic hormone, WBRKeyword::ADH, WBRKeyword::hormones
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