Question

How does DAG vs. IP3 result in different signaling options?  How do they both feed into Protein Kinase C activation?

How does Ca²⁺function in the cell in response to ER release? What are two examples of targets that Ca²⁺ can bind?

Answer 1

Together with diacylglycerol (DAG), IP3 (ionositol phosphate) is a second messenger molecule used in signal transduction in biological cells. Here, DAG stays inside the membrane, IP3 is soluble and diffuses through the cell, where it binds to its receptor, which is a calcium channel located in the endoplasmic reticulum. When IP3 binds its receptor, calcium is released into the cytosol, thereby activating various calcium regulated intracellular signals.

Protein kinase C (PKC) belongs to a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups . PKC enzymes in turn are activated by signals such as increases in the concentration of diacylglycerol (DAG) or calcium ions (Ca2+). Hence PKC enzymes play important roles in several signal transduction cascades.The endoplasmic reticulum is a major storage compartment for calcium ions. Calcium is involved in many cellular activities because it interacts with proteins, helping them do their jobs. Knowing how calcium release affects activities such as muscle contraction and cell death will help you understand why the release must be controlled. The endoplasmic reticulum has calcium channels on its surface that regulate the outflow of calcium ions. These channels can be opened by electrical signals or activating molecules. No matter what method is used to open these channels, the method must be tightly controlled by the cell because calcium does so many things once released.

Examples - calmodulin, tubulin.