Session Type: Abstract Submissions (ACR)
GPSM3, a newly described regulator of heterotrimeric G protein signaling, is selectively expressed in hematopoietic cells with high expression in monocytes. We have shown that Gpsm3 deficient (-/-) mice are protected from Collagen Antibody Induced Arthritis due in part to their attenuated monocyte responses, including decreased ex vivo migration to the chemokines CX3CL1, CCL2, and chemerin, and enhanced apoptosis, which leads to an observed decrease in proinflammatory intra-articular IL-6 and IL-1b transcripts in the joint. Given the restricted expression of GPSM3 in leukocytes and the functional phenotypes observed in immune cells lacking GPSM3 expression, we chose to examine effects of GPSM3 deficiency in Collagen Induced Arthritis (CIA) and to analyze whether single nucleotide polymorphisms (SNPs) within the human GPSM3 gene locus, associated with a decreased incidence of autoimmunity, correlate with altered GPSM3 gene products.
Gpsm3-/- and Gpsm3+/+ DBA1-J mice were immunized with heterologous type II collagen in Freund’s Adjuvant with a booster immunization at day 21 per published protocols. Arthritis was assessed by a blinded observer for paw swelling and clinical disease score (0-4). Paws were processed at day 42 for histopathology. Serum B-cell activating factor (BAFF) was measured by commercial ELISA (R&D Systems) per manufacturer’s instructions on day 14. DNA and RNA was isolated from healthy human subject blood using Qiagen purification reagents. Genotyping for SNP (A (minor) / G (major) transition substitution) was performed using commercially available TaqMan SNP Genotyping Assay (SNP ID = rs204989) from Applied Biosystems by Life Technologies. qRT-PCR primers for known GPSM3 transcripts -001, -002, -003, and -004 were designed from NCBI (-001 and -002) and Ensembl (-003 and -004) databases, and validated by gel electrophoresis for sequence length, sequencing, melt curve analysis, and PrimerBlast. qRT-PCR of cDNA from healthy human subject blood was performed using a Biorad CFX96 Real-Time System and standard protocols. Data was calculated as relative expression compared to the housekeeping gene IDUA(ΔCt).
Gpsm3-/- mice are protected from CIA and have significantly decreased serum BAFF levels. Healthy human subjects carrying protective SNP alleles that correlate with a decreased incidence of rheumatoid arthritis (RA) and four other autoimmune diseases have decreased levels of transcripts GPSM3-001, -002, and -004, but significantly increased levels of the transcript GPSM3-003, which is thought to be subjected to nonsense-mediated decay.
Our goal from these studies is to determine whether GPSM3 has immune system-modulating potential for the treatment of autoimmune diseases with particular focus on inflammatory arthritis. Gpsm3-/- mice are protected from two models of inflammatory arthritis through mechanisms involving monocyte function. GPSM3 has altered mRNA transcripts in healthy human subjects with SNPs that correlate with decreased RA and other autoimmune diseases, suggesting differential gene regulation.
T. K. Tarrant,
D. S. Serafin,
M. J. Billard,
D. P. Siderovski,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/g-protein-signaling-modulator-3-gpsm3-deficiency-is-protective-in-inflammatory-arthritis-models-and-altered-gpsm3-gene-products-correlate-with-single-nucleotide-polymorphisms-in-humans/