Gβ5 is the only G protein β-subunit specifically expressed in neuronal cells. A splice variant of Gβ5 which is longer than Gβ5 by 40 amino acids (Gβ5L) is only expressed in photoreceptors (1). Here, we studied the localization of the two forms in more detail and investigated its dependence on light. Immunohistochemical staining of sections of dark-adapted mouse retinas revealed Gβ5 immunoreactivity in the inner (INL) and outer (ONL) nuclear layers as well as in the outer segments (OS). In the light-adapted tissue, the staining in the ONL and OS was dramatically reduced. Intact bovine OS, purified by ultracentrifugation, contained only GβSL, while Gβ5 (short) was mainly found in the soluble lysate of retina. A small fraction of Gβ5 was also associated with membranes that did not contain rhodopsin and most likely originated from non-photoreceptor cells. To begin the identification of other members of the Gβ5-mediated pathway, we purified the native complex of soluble Gβ5 to near homogeneity. Gβ5 is coupled to a 10 kDa protein, apparently a Gy subunit. This Gy is, however, distinct from the y subunit of transducin (Gyl) as well as from Gy2, Gv3, Gy5 and Gy7. Unexpectedly, we found that the native complex does not contain any known Get subunits or phosducin, but rather a yet unidentified 65 kDa protein. Identification of the two Gβ5-associated proteins is now in progress. 1. Watson, J.A., Aragay, A.M., Siepak, V.Z., Simon, M.I. A novel form of the G protein βsubunit Gβ5 specifically expressed in vertebrate retina (1996) J. Biol. Chem.. 271, 28154. & American Heart Association (9603008); Stanley Glaser Foundation; # Researh to Prevent Blindness; Ruth and Milton Steinbach Fund.
|Original language||English (US)|
|State||Published - Dec 1 1998|
ASJC Scopus subject areas
- Molecular Biology