Genetic variations in GPSM3 associated with protection from rheumatoid arthritis affect its transcript abundance

Abstract

G protein signaling modulator 3 (GPSM3) is a regulator of G protein-coupled receptor signaling, with expression restricted to leukocytes and lymphoid organs. Previous genome-wide association studies have highlighted single-nucleotide polymorphisms (SNPs rs204989, rs204991) in a region upstream of the GPSM3 transcription start site as being inversely correlated to the prevalence of rheumatoid arthritis (RA) -- this association is supported by the protection afforded to Gpsm3-deficient mice in models of inflammatory arthritis. Here, we assessed the functional consequences of these polymorphisms. We collected biospecimens from 50 volunteers with RA diagnoses, 50 RA-free volunteers matched to the aforementioned group, and 100 unmatched healthy young volunteers. We genotyped these individuals for GPSM3 (rs204989, rs204991), CCL21 (rs2812378), and HLA gene region (rs6457620) polymorphisms, and found no significant differences in minor allele frequencies between the RA and disease-free cohorts. However, we identified that individuals homozygous for SNPs rs204989 and rs204991 had decreased GPSM3 transcript abundance relative to individuals homozygous for the major allele. In vitro promoter activity studies suggest that SNP rs204989 is the primary cause of this decrease in transcript levels. Knockdown of GPSM3 in THP-1 cells, a human monocytic cell line, was found to disrupt ex vivo migration to the chemokine MCP-1.

Reduction of GPSM3 expression akin to the arthritis-protective SNP rs204989 differentially affects migration in a neutrophil model

“…, in the absence of Gβγ subunits), as has been speculated on recently by Blumer and colleagues ( 32 ). The effect of GPSM3 deficiency on NB4* LTB4-induced migration, coupled with the established role that LTB4 plays in the early pathogenesis of RA, supports the therapeutic potential of GPSM3-targeted inhibitors in the treatment of RA, as we have proposed previously ( 11 ); the potential to inhibit GPSM3 pharmacologically and thereby reduce neutrophil migration to the inflammed joint while sparing fMLP responsiveness is attractive as it suggests a means of reducing RA pathology without compromising responsiveness to bacterial infections.…”

“…As signaling by the free Gβγ heterodimer is central to the migratory response ( 22 , 23 ), any accelerated deactivation by increased Gα i reassociation would lead to a diminished migration phenotype. Given the diminished NB4* cell line migration toward the RA-relevant chemoattractants LTB4 and CXCL8, we surmise that the synovial acellularity seen in anti-collagen antibody challenged GPSM3-deficient mice ( 12 ) and the inverse association between RA development and the GPSM3 expression-lowering SNP rs204989 ( 11 ) could be the result of reduced neutrophil recruitment by these particular chemoattractants.…”

“…, NCBI GEO accession number GSE62408 ( 28 )). These findings sparked our interest in determining whether GPSM3 regulates aspect(s) of neutrophil biology, especially in light of the GPSM3 SNP rs204989 being associated with decreased GPSM3 expression ( 11 ) and protection against the development of rheumatoid arthritis ( 5 – 7 ) – an autoimmune disease in which neutrophil function is central to its initiation. Using RNA-interference to negate the GPSM3 upregulation found to occur normally in the promyelocytic NB4 cell line upon ATRA differentiation, we have now established that GPSM3 is required for the full migratory response of this neutrophil-like cell line toward a pathophysiologically relevant concentration of LTB4 ( 29 ); in addition, GPSM3 also appears to play a role in migratory responsiveness toward CXCL8, although only observed with the highest degree of GPSM3 deficiency ( i.e.…”

“…( 10 )). We recently reported ( 11 ) that SNPs rs204989, rs204990, and rs204991 constitute a haplotype block within which the rs204989 C>T transition is causal to reduced GPSM3 promoter activity. The association between a promoter-weakening GPSM3 SNP and reduced risk of RA is supported by the protection afforded to Gpsm3 -deficient mice in an acute model of inflammatory arthritis ( 12 ).…”

Genetic and Pharmacologic Studies Towards Prevention of opioid use disorder

“…West Virginia is the epicenter of this opioid crisis, leading in opioid-related overdose deaths (Seth et al, 2018). The state is also demographically homogenous (Gall et al, 2016) Lander et al, 2013;Zheng et al, 2017). Given access to this WV patient population, we sought to address whether there are single nucleotide polymorphisms (SNPs) more or less prevalent in WV persons with OUD than in the general population.…”