WBR0444

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Physiology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A researcher is studying the pathways that anti-diuretic hormone (ADH) undergoes before hormonal effect takes place. Following release from the supraoptic nuclei in the posterior hypothalamus, the researcher follows the signaling pathways of ADH V2. 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::G-coupled receptor pathway that eventually activates protein kinase A is the signaling pathway of ADH V2.
Answer B	AnswerB::Receptor or intrinsic tyrosine kinase signaling pathway that eventually utilizes adapter protein
Answer B Explanation	AnswerBExp::This pathway is utilized by insulin and other growth factors, 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 activates leads to 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. It is important to note that the signaling pathway utilized by ADH V2 is different from ADH V1. ADH V2 receptor activates the Gs-coupled receptor pathway that activates adenylyl cyclase. The latter catalyzes the conversion of ATP to cyclic AMP (cAMP) that activates protein kinase A. On the other hand, ADH V1 utilizes another signaling pathway; the Gq-coupled receptor pathway that activates phospholipase C and ultimately leads to formation of inositol triphosphate (IP3) and diacyl glycerol (DAG) and activation of protein kinase C. Educational Objective: ADH V2 receptor activates the Gs-coupled receptor pathway that activates adenylyl cyclase. The latter catalyzes the conversion of ATP to cyclic AMP (cAMP) that activates protein kinase A. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::signaling, WBRKeyword::pathway, WBRKeyword::G couple, WBRKeyword::receptor, WBRKeyword::protein, WBRKeyword::kinase A, WBRKeyword::Anti, WBRKeyword::diuretic, WBRKeyword::hormone, WBRKeyword::ADH
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