What function is described for ZO-2 proteins?

• A. Mediate actin binding
• B. Phagocytosis
• C. Responds to epidermal GF signaling
• D. Secretion of mucus

Answer: (C)

ZO-2 proteins act as tight junction scaffolds that also participate in signaling at the cell junctions. A key described function is their involvement in responding to epidermal growth factor signaling, meaning they help translate growth-factor cues into cellular responses while coordinating junctional integrity. This signaling role ties into how tight junctions regulate not just the barrier but also gene expression and cell behavior, such as through interactions that can influence transcription factors and proliferation.

Phagocytosis and mucus secretion aren’t functions associated with ZO-2 proteins, and while tight junctions connect to the actin cytoskeleton, their defining role isn’t to mediate actin binding directly. The emphasis for ZO-2 is their participation in signaling at the junctions in response to growth factor cues.