Cell Signalling and Receptor Mechanisms · USMLE Step 1

A growth factor binds to its receptor on a target cell. Subsequently, the receptor dimerizes and phosphorylates itself. Which downstream effect is most consistent with this mechanism?

  1. Rapid Na⁺ influx producing immediate membrane depolarization
  2. cAMP-mediated activation of protein kinase A (PKA)
  3. A phosphorylation cascade that alters gene expression
  4. Immediate opening of a membrane chloride (Cl⁻) channel
Show answer and explanation

Correct answer: A phosphorylation cascade that alters gene expression

Growth factor receptors are often RTKs; their autophosphorylation initiates kinase cascades (e.g. MAPK) that lead to changes in gene expression and cell behavior.

Difficulty: Medium Question 18 of 22

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