Regulator of G protein signaling 9-2 (RGS9-2) mRNA is up regulated during neuronal differentiation of mouse embryonic stem cells

The Potential Role of R4 Regulators of G Protein Signaling (RGS) Proteins in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a complex and heterogeneous disease that primarily results from impaired insulin secretion or insulin resistance (IR). G protein-coupled receptors (GPCRs) are proposed as therapeutic targets for T2DM. GPCRs transduce signals via the Gα protein, playing an integral role in insulin secretion and IR. The regulators of G protein signaling (RGS) family proteins can bind to Gα proteins and function as GTPase-activating proteins (GAP) to accelerate GTP hydrolysis, thereby terminating Gα protein signaling. Thus, RGS proteins determine the size and duration of cellular responses to GPCR stimulation. RGSs are becoming popular targeting sites for modulating the signaling of GPCRs and related diseases. The R4 subfamily is the largest RGS family. This review will summarize the research progress on the mechanisms of R4 RGS subfamily proteins in insulin secretion and insulin resistance and analyze their potential value in the treatment of T2DM.

Regulator of G protein signaling transcript expression in human neural progenitor differentiation: R7 subfamily regulation by DNA methylation

G protein-coupled receptors (GPCRs) and their ligands are critical regulators of neural progenitor differentiation, and GPCR signaling pathways are regulated by regulator of G protein signaling (RGS) proteins. RGS protein expression is dynamically regulated, and we have recently described the epigenetic regulation of RGS transcript expression. Given the potential of RGS proteins to regulate GPCR signaling and the established role of epigenetic regulation in progenitor differentiation, we explored the impact of epigenetic regulation of RGS transcripts during in vitro differentiation of human neural progenitors. Here, we demonstrate robust upregulation of the RGS transcripts RGS4, RGS5, RGS6, RGS7, and RGS11 during neuronal differentiation, while DNA methyltransferase (DNMT) and histone deacetylase enzyme expression is suppressed during differentiation. Transcripts encoding R7 subfamily RGS proteins and the R7-binding partners R7BP and R9AP showed the greatest upregulation. Further, we showed that direct pharmacological inhibition of DNMT activity enhances expression of RGS2, RGS4, RGS5, RGS6, RGS7, RGS8, RGS9L, RGS10, and RGS14 as well as R7BP and R9AP transcripts in progenitors, consistent with regulation by DNMTs. Our results reveal marked upregulation of RGS expression during neuronal differentiation and suggest that decreased expression of DNMT enzymes during differentiation contributes to upregulation.

Organic cation transporter-mediated ergothioneine uptake in mouse neural progenitor cells suppresses proliferation and promotes differentiation into neurons

The aim of the present study is to clarify the functional expression and physiological role in neural progenitor cells (NPCs) of carnitine/organic cation transporter OCTN1/SLC22A4, which accepts the naturally occurring food-derived antioxidant ergothioneine (ERGO) as a substrate in vivo. Real-time PCR analysis revealed that mRNA expression of OCTN1 was much higher than that of other organic cation transporters in mouse cultured cortical NPCs. Immunocytochemical analysis showed colocalization of OCTN1 with the NPC marker nestin in cultured NPCs and mouse embryonic carcinoma P19 cells differentiated into neural progenitor-like cells (P19-NPCs). These cells exhibited time-dependent [³H]ERGO uptake. These results demonstrate that OCTN1 is functionally expressed in murine NPCs. Cultured NPCs and P19-NPCs formed neurospheres from clusters of proliferating cells in a culture time-dependent manner. Exposure of cultured NPCs to ERGO or other antioxidants (edaravone and ascorbic acid) led to a significant decrease in the area of neurospheres with concomitant elimination of intracellular reactive oxygen species. Transfection of P19-NPCs with small interfering RNA for OCTN1 markedly promoted formation of neurospheres with a concomitant decrease of [³H]ERGO uptake. On the other hand, exposure of cultured NPCs to ERGO markedly increased the number of cells immunoreactive for the neuronal marker βIII-tubulin, but decreased the number immunoreactive for the astroglial marker glial fibrillary acidic protein (GFAP), with concomitant up-regulation of neuronal differentiation activator gene Math1. Interestingly, edaravone and ascorbic acid did not affect such differentiation of NPCs, in contrast to the case of proliferation. Knockdown of OCTN1 increased the number of cells immunoreactive for GFAP, but decreased the number immunoreactive for βIII-tubulin, with concomitant down-regulation of Math1 in P19-NPCs. Thus, OCTN1-mediated uptake of ERGO in NPCs inhibits cellular proliferation via regulation of oxidative stress, and also promotes cellular differentiation by modulating the expression of basic helix-loop-helix transcription factors via an unidentified mechanism different from antioxidant action.