13. You discover a signal transduction pathway onyerizon. SigC is the ligand, wh

Question

13. You discover a signal transduction pathway onyerizon. SigC is the ligand, which binds to and activates a receptor that regulates actin rosine kinase (RTK). Activation of the RTK leads to the activation of the Ras protein, which then activates the protein kinase PK1 that phosphorylates the RingA protein on S34. When phosphorylated, RingA binds to the gene regulatory protein, AP1. When RingÀ is bound to AP1, AP1 can enter the nucleus and bind to DNA to ty SigC activate XTRACILLULAR transcription of the SPACAL ARP2/ARP3 complex, leading to increased actin polymerization in the cell. A portion of this ilvsted RTM signal transduction pathway is diagrammed in the Figure. inactive Ras protein activated Ras protein For each of the situations below, indicate whether you predict actin polymerization w increase, decrease, or stay the same compared to normal cells that are grown in the prese of SigC. nce a. The cell has a constitutively active Ras protein instead of normal Ras. 01 A hayden-m

Explanation / Answer

a. Constitutively active Ras will lead to increased actin polymerization and gene expression would not get shut.

b. Mutation will lead to no phosphorylation, hence abrogation of actin polymerization.

c.No SigC binding means no downstream signaling and correspondingly no actin polymerization.

d.There will be increased actin polymerization due to an increased activity of PK1.

e.Cytoplasmic domain that cannot be phosphorylated would not lead to dimerization. As a result further downstream signalling would not take place leading to an abrogation of actin polymerization provided RTK pathway is the only one responsible for the process.

f. The downstream signaling gets affected, hence actin polymerization might be reduced or stopped.

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