Abstract
The present study investigated G protein expression, localization, and functional coupling to thromboxane A2 receptors (TPRs) during oligodendrocyte (OLG) development. It was found that as OLGs mature, the expression levels of Gq increase while those of G13 decrease. In contrast, the expression levels of Gs, Go, and Gi do not change significantly. Localization studies revealed that Gq, G13, and Gi are present only in the extranuclear compartment, whereas Gs and Go are found in both the extranuclear and the nuclear compartments. Purification of TPR-G protein complexes demonstrated that TPRs couple to both Gq and G13 in the extranuclear compartment but only to Gs in the nuclear compartment. Furthermore, functional analysis revealed that stimulation of nuclear TPR in OLGs stimulates CREB phosphorylation and myelin basic protein transcription and increases survival. Collectively, these results demonstrate that (i) OLGs selectively modulate the expression of certain G proteins during development, (ii) G proteins are differentially localized in OLGs leading to subcellular compartmentalization, (iii) TPRs couple to Gq and G13 in the extranuclear compartment and to Gs only in the nucleus, (iv) mature OLGs have a functional nuclear TPR-Gs signaling pathway, and (v) nuclear TPR signaling can stimulate CREB phosphorylation and myelin gene transcription and increase cell survival. These findings represent a novel paradigm for selective modulation of G protein-coupled receptor-G protein signaling during cell development.
ACKNOWLEDGMENTS
We thank S. Srinivasan and J.-S. Huang for assistance with the cAMP assay and L. Dong for her help with primary cell culture. We also thank F. Khaswaneh for critical reading of the manuscript.
This work was supported in part by a grant from the National Multiple Sclerosis Society (RG 3054B2/1) awarded to G.C.L.