Question

Which of the following statements are TRUE for phosphoinositide signaling cascade?

• A. Phospholipase A catalyzes cleavage of PIP2
• B. Generation of IP\(_3\) transiently increases cytosolic Ca\(^{2+}\) concentration
• C. Ca\(^{2+}\) facilitates the activation of protein kinase C
• D. DAG always activates protein kinase A

Hint:

In the phosphoinositide signaling pathway, IP3 increases intracellular Ca\(^{2+}\), while DAG activates PKC, not PKA.

Answer 1

The Correct Option is B, C

Step 1: Understanding the phosphoinositide signaling cascade.
The phosphoinositide signaling pathway involves the activation of phospholipase C (PLC), which cleaves PIP2 (phosphatidylinositol 4,5-bisphosphate) into IP3 (inositol trisphosphate) and DAG (diacylglycerol). IP3 stimulates the release of Ca\(^{2+}\) from intracellular stores, while DAG activates protein kinase C (PKC).

Step 2: Analyzing the options.
(A) Phospholipase A catalyzes cleavage of PIP2: This is incorrect. Phospholipase C, not A, cleaves PIP2 into IP3 and DAG.
(B) Generation of IP\(_3\) transiently increases cytosolic Ca\(^{2+}\) concentration: This is correct. IP3 activates the IP3 receptor, leading to the release of Ca\(^{2+}\) from the endoplasmic reticulum.
(C) Ca\(^{2+}\) facilitates the activation of protein kinase C: This is correct. Ca\(^{2+}\) helps activate protein kinase C (PKC), which is involved in various cellular responses.
(D) DAG always activates protein kinase A: This is incorrect. DAG activates PKC, not protein kinase A (PKA).

Step 3: Conclusion.
The correct answer is (B) Generation of IP\(_3\) transiently increases cytosolic Ca\(^{2+}\) concentration, as this accurately describes the role of IP3 in phosphoinositide signaling.