Fertilization Signal Transduction
During sea urchin egg fertilization, the sperm binds to a receptor on the egg plasma membrane. The sperm receptor is coupled to a G-protein. When occupied, this receptor causes the activation of Phospholipase C which hydrolyzes PIP2 into IP3 and DAG. DAG remains within the membrane and activates Protein Kinase C. IP3 moves into the cytoplasm and binds to an IP3 receptor on the ER membrane allowing for the release of Ca2+ into the egg cytoplasm.
(courtesy of Dr. J. Hardin, Univ. of Wisconsin)
- Take a humorous look at the IP3-Ca++ signal transduction pathway. (courtesy of Dr. A. Malcolm Campbell, Davidson College) IP3 and Ca++ (Shockwave Flash .swf)
A fluorescent calcium indicator was microinjected into an egg and then the egg was fertilized. This movie shows that the release and transient increase in free cytosolic calcium travels in a wave from the point of sperm entry (2 o'clock) to the opposite side of the egg. (8 o'clock)