The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-beta on melanosomes.

Protein kinase C (PKC), a family of at least eleven isoforms, mediates numerous cell functions. In human melanocytes, alpha, beta, delta, epsilon and zeta isoforms of PKC are expressed, but uniquely PKC-beta activates tyrosinase, the key and the rate-limiting enzyme in melanogenesis, by phosphorylating specific serine residues on its cytoplasmic domain. To investigate the mechanism by which only PKC-beta phosphorylates tyrosinase, we examined the expression of receptor for activated C-kinase-I (RACK-I), a receptor specific for activated PKC-beta, on the surface of melanosomes, the specialized organelle in which melanogenesis occurs. Immunoblot analysis of purified melanosomes revealed that RACK-I is readily detectable. Immunoprecipitation of RACK-I from purified melanosomes, followed by immunoblot analysis using antibody against PKC-beta, revealed abundant PKC-beta, whereas PKC-alpha was not detected when immunoblot analysis was performed using antibody against PKC-alpha. Activation of PKC in melanocytes increased the level of PKC-beta co-immunoprecipitated with RACK-I, while the level of melanosome-associated RACK-I decreased when melanocytes were treated chronically with the 12-0-tetradecanoyl-phorbol 13-Acetate (TPA), a condition known to deplete PKC and reduce tyrosinase activity. Immunoprecipitation with RACK-I antibody co-precipitated fewer PKC-beta in the presence of UV-activated 1, 1'-decamethylenebis-4-aminoquinaldinium di-iodide (DECA), known to disrupt the interaction between activated PKC-beta and RACK-I. Treatment of intact melanocytes with DECA also decreased tyrosinase activity. Moreover, suppression of RACK-I expression by transfecting melanocytes with siRNA against RACK-I reduced the basal tyrosinase activity and blocked TPA-induced increases in tyrosinase activity. Taken together, these results demonstrate that RACK-I anchors activated PKC-beta on the melanosome membrane, allowing PKC-beta to phosphorylate tyrosinase.[1]


  1. The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-beta on melanosomes. Park, H.Y., Wu, H., Killoran, C.E., Gilchrest, B.A. J. Cell. Sci. (2004) [Pubmed]
WikiGenes - Universities