Transforming growth factor-beta (TGF-β) signals through receptor serine/threonine kinases. Which intracellular mediator is directly phosphorylated by the TGF-β type I receptor and then translocates to the nucleus to regulate gene transcription?

• A SMAD2/3 ✓
• B STAT5
• C β-catenin
• D NF-κB

Explanation

TGF-β binds to the type II receptor, which recruits and phosphorylates the type I receptor. The type I receptor then phosphorylates receptor-regulated SMADs (SMAD2 and SMAD3). These associate with SMAD4, translocate to the nucleus, and regulate transcription of target genes. STAT5 is for cytokine receptors, β-catenin for Wnt signaling, and NF-κB is activated by inflammatory pathways.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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