Zinedin, SG2NA, and striatin are calmodulin-binding, WD repeat proteins principally expressed in the brain

Striatin is an intracellular protein characterized by four protein-protein interaction domains, a caveolin-binding motif, a coiled-coil structure, a c almodulin-binding domain, and a WD repeat domain, suggesting that it is a s ignaling or a scaffold protein. Down-regulation of striatin, which is expre ssed in a few subsets of neurons, impairs the growth of dendrites as well a s rat locomotor activity (Bartoli, M., Ternaux, J. P., Forni, C., Portalier , P., Salin, P., Amalric, M,, and Monneron, A. (1999) J. Neurobiol. 40, 234 -243). Zinedin, a "novel" protein described here, and SG2NA share with stri atin identical protein-protein interaction domains and the same overall dom ain structure. A phylogenetic analysis supports the hypothesis that they co nstitute a multigenic family deriving from an ancestral gene. DNA probes an d antibodies raised against specific domains of each protein showed that zi nedin is mainly expressed in the central nervous system, whereas SG2NA, of more widespread occurrence, is mainly expressed in the brain and muscle. Al l three proteins are both cytosolic and membrane-bound. All three bind calm odulin in the presence of Ca2+. In rat brain, SG2NA and striatin are genera lly not found in the same neurons. Both localize to the soma and dendrites, suggesting that they share a similar type of addressing and closely relate d functions.