G‐protein γ7 subunit is selectively expressed in medium‐sized neurons and dendrites of the rat neostriatum

Abstract

We used subtractive hybridization to isolate clones of gamma 7, a 68 residue G-protein gamma subunit. Northern blotting and in situ hybridization reveal that the gamma 7 subunit mRNA is expressed primarily in medium-sized neurons of the neostriatum and nucleus accumbens and neurons of the olfactory tubercle, and at low levels in the dentate gyrus of the hippocampal formation and laminae II-III, and V of the neocortex. The gamma 7 mRNA is translocated into dendrites of neurons in the neostriatum and the dentate gyrus of the hippocampus. gamma 7 is expressed at relatively very low concentrations in peripheral tissues. The selective pattern of gamma 7 expression within the brain is highly reminiscent of those of the striatum-enriched adenylyl cyclase ACST, dopamine receptors, and the alpha subunit of G(olf), suggesting that, in striatum, gamma 7 may be a subunit of a G(olf) alpha-containing G protein that couples dopamine receptors selectively to ACST.

Differential Dependence of the D1 and D5Dopamine Receptors on the G Protein γ7 Subunit for Activation of Adenylylcyclase

“…Dependence of the D 1 Dopamine Receptor Subtype on the G Protein ␥ 7 Subunit for Activation of Adenylylcyclase ActivityThe D 1 dopamine receptor, the G protein ␥ 7 subunit, and adenylylcyclase are highly expressed in striatum (4,12,13,29,30,31), suggesting that these components may be involved in the same signaling pathway. This possibility is supported by the finding that the D 1 dopamine receptor-expressing cells transfected with the wild type ␥ 7 ribozyme showed a 32% reduction in SKF21897-induced cAMP accumulation (Fig.…”

“…However, in support of this possibility, we used reverse transcriptase-PCR analysis of individual, striatal neurons (31,32) to show that the D 1 dopamine receptor and G protein ␥ 7 subunit are predominantly and coordinately expressed in SP containing neurons that project to the substantia nigra par reticulata. Intriguingly, the Gng7 locus encoding the G protein ␥ 7 subunit has been localized to mouse chromosome 10 in the vicinity of several neurological mutations, such as jittery, Ames Waltzer, and mocha (13). Thus, on the basis of these findings, the G protein ␥ 7 subunit should be considered as a candidate for these and other genetic disorders that map near this region in the future.…”

“…Although sharing 88% amino acid homology, the ␣s and ␣ olf subunits show very divergent expression patterns, ranging from the ubiquitous expression of the ␣ s subunit to the olfactory and neuron-specific expression of the ␣ olf subunit (10). Immunoprecipitation studies (11) have confirmed the interaction between the ␣ s subunit and the D 1 dopamine receptors in cells, whereas in situ hybridization (12,13) and gene targeting (14) studies have suggested a possible interaction between the ␣ olf subunit and the D 1 dopamine receptor in striatum.…”

“…This approach identified the ␥ 7 subunit as a specific component of the G protein that couples the ␤-adrenergic receptor, but not the prostaglandin E 1 receptor, to stimulation of adenylylcyclase in HEK 293 cells (23). Although expressed in a variety of tissues and cell types (27,28), the ␥ 7 subunit expression is most abundant in medium spiny neurons in striatum (13). This pattern of expression is shared by the D 1 dopamine receptor and adenylylcyclase (4, 12, 29 -31), raising the possibility that all of these components may be involved in the same signaling pathway.…”

A Novel Form of the G Protein β Subunit Gβ5 Is Specifically Expressed in the Vertebrate Retina

“…For example, specificity in visual signal transduction by the light receptor, rhodopsin, is mediated in part by tissue-and cell type-specific expression of rod and cone cell G␣ and G␥ subunits (4). Somatic compartmentalization of other G protein ␣ and ␥ subunits has been described (5,6). To date, G␤ 5 , which is readily detected only in the central nervous system, is the only G protein ␤ subunit known to be expressed in a tissuerestricted fashion (7).…”