RGS4 Regulates Neurite Outgrowth And Cell Proliferation Mediated by STAT5B Transcriptional Responses

Abstract

Regulators of G proteins signaling (RGS) serve several cellular functions, despite their initial role as GTPase activating proteins. Recent evidence suggests that RGS proteins interact with transcription factors to mediate transcriptional responses. RGS4, a member of the B/R4 family of RGS proteins, is a multitask protein highly expressed in developing neurons, that has been shown to be a key regulator of opioid receptor signaling (ORs) by confering selectivity for G protein coupling, inhibiting OR‐mediated ERK1,2 phosphorylation and accelerating receptor internalization (Leontiadis et al. 2009; Georgoussi et al. 2006). We have previously shown that δ‐OR forms a multiprotein signaling complex, consisting of Gi/Go proteins and the Signal Transducer and Activator of Transcription 5B (STAT5B) that leads to neurite outgrowth upon DSLET‐δ‐OR activation (Georganta et al. 2010;2013). Based on these findings and the fact that RGS4 directly interacts with STAT5B to negatively regulate STAT5B activation (Pallaki et al. 2017) we wondered whether RGS4‐STAT5B interplay could be involved in cellular mechanisms controlling neurogenesis.Primary neuronal cortical cultures from RGS4−/− mice, lacking a functional RGS4, exhibited differential neuronal sprouting compared to wild types, as assessed by an increased axonal length and branch number, upon DSLET administration. Additional studies in brain extracts from adult RGS4−/− mice demonstrated increased levels of phospho‐STAT5B while exhibited altered expression levels of STAT5B inducible genes Snx9 and Ptk2 which are both highly implicated in axonogenesis. This result indicates that RGS4 is implicated in neurite outgrowth via a STAT5B‐mediated transcriptional regulation. On the other hand, Neuro2A cells stably expressing RGS4 exhibited a significant reduction in the cell number and proliferation rate whereas isolated RGS4−/− neural stem cells exhibited elevated proliferative properties with a concomitant increase of the mRNA levels of the STAT5B anti‐apoptotic target genes, Bcl‐2 and Bcl‐xl. The same expression pattern was also confirmed in RGS4−/− mature adult brain tissues. Collectively, these studies demonstrate for the first time a novel selective role of RGS4 in STAT5B mediated‐transcriptional responses providing insights into the role of RGS4 involvement in neuronal development and synaptic signaling upon δ‐opioid administration.Support or Funding InformationThis work was supported by grants NORMOLIFE (LSHC‐CT037733) and the GSRT Excellence II, 3722 ‐”NO‐ALGOS” to Z.G. The facilities of the Hellenic Research Infrastructure OPENSCREEN‐GR were used for protein expression.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.