Signal transduction in sea-urchin sperm chemotaxis

Description:

Description: English: A model of the signal-transduction pathway during chemotaxis of the sea urchin Arbacia punctulata. Binding of a chemoattractant (ligand) to the receptor — a membrane-bound guanylyl cyclase (GC) — activates the synthesis of cGMP from GTP. Cyclic GMP possibly opens cyclic nucleotide-gated (CNG) K+-selective channels, thereby causing hyperpolarization of the membrane. The cGMP signal is terminated by the hydrolysis of cGMP through phosphodiesterase (PDE) activity and inactivation of GC. On hyperpolarization, hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels allow the influx of Na+ that leads to depolarization and thereby causes a rapid Ca2+ entry through voltage-activated Ca2+ channels (Cav), Ca2+ ions interact by unknown mechanisms with the axoneme of the flagellum and cause an increase of the asymmetry of flagellar beat and eventually a turn or bend in the swimming trajectory. Ca2+ is removed from the flagellum by a Na+/Ca2+ exchange mechanism. [Taken from (Kaupp et al., 2006).]. Date: 2006. Source: ftp://ftp.weizmann.ac.il/incoming/Fig.1.jpg. Author: Prof. Dr. U.B. Kaupp. Permission(Reusing this file): ftp://ftp.weizmann.ac.il/incoming/License_for_Fig1.pdf. : All biology images in this gallery could be re-created using vector graphics as SVG files. This has several advantages; see Commons:Media for cleanup for more information. If an SVG form of this image is available, please upload it and afterwards replace this template with {{vector version available|new image name}}.