Horrigan, F. T. | Search bioRxiv

bioRxiv2026

The L-type voltage-gated Ca2+ channel CaV1.2 regulates fibroblast-like synoviocytes invasiveness during rheumatoid arthritis

Fibroblast-like synoviocytes (FLS) are major drivers of synovial tissue inflammation and damage during rheumatoid arthritis (RA). A hallmark of the aggressiveness of RA-FLS is their invasiveness but the molecular mechanisms that regulate this invasiveness remain poorly understood. The KCa1.1 (BK, Slo1, MaxiK, KCNMA1) potassium channel is a major regulator of RA-FLS pathogenicity and inhibiting KCa1.1 expression or its activity with selective blockers reduces RA-FLS invasiveness and reduces disease severity and joint damage in rat models of RA. KCa1.1 blockade induces a Ca2+ influx in RA-FLS whose intracellular signaling results in increased cell adhesion to the extracellular matrix and thus a reduction in cell migration. However, the identity of the Ca2+-permeable channel responsible for the Ca2+ influx has remained elusive. Here, we demonstrate the co-expression of KCa1.1 with the L-type voltage-gated CaV1.2 channels at the plasma membrane of primary human and rat FLS. Selective blocking of the CaV1.2 channel blunts the Ca2+ influx induced by KCa1.1 blockade and abrogates the effects of KCa1.1 blockade on RA-FLS invasiveness, migration, cell shape, and podoplanin expression. Whereas KCa1.1 blockers reduce disease severity in rat models of RA, treating rats with the collagen-induced arthritis model of RA with both blockers of KCa1.1 and CaV1.2 eliminates the therapeutic benefits of treatment with KCa1.1 blockers alone. Together, these data demonstrate a physical and functional coupling of KCa1.1 and CaV1.2 channels in FLS during RA and its rat model that regulate the invasive phenotype of the FLS through modulation of intracellular Ca2+ homeostasis.

cell biology↗

bioRxiv2018

Discovery of a bacterial peptide as a modulator of GLP-1 and metabolic disease

Early work in germ-free rodents highlighted the gut microbiotas importance in metabolic disease, including Type II Diabetes Mellitus (T2DM) and obesity. Glucagon-like peptide-1 (GLP-1) is an incretin secreted by enteroendocrine L-cells lining the gastrointestinal epithelium. GLP-1 has important functions including promoting insulin secretion, insulin sensitivity, and {beta}-cell mass, while inhibiting gastric emptying and appetite. We set out to elucidate how the microbiota can modulate GLP-1 secretion, with the goal to identify microbial strains with GLP-1 stimulatory activity as a metabolic disease therapeutic. Over 1500 human-derived strains were isolated from fecal, breast milk, and colon and intestinal biopsy samples from healthy individuals. In vitro screening for GLP-1 modulation was performed by incubating bacterial cell-free supernatants with NCI H716 human L-cells. Approximately 45 strains capable of increasing GLP-1 levels, measured by ELISA, were discovered. Interestingly, all positive strains were identified as Staphylococcus epidermidis by 16S rRNA sequencing. Non-GLP-1 stimulatory S. epidermidis strains were also identified. Mass spectrometry analysis identified a 3 kDa peptide, termed GLP-1 stimulating peptide (GspA), present in GLP-1 positive but absent in GLP-1 neutral S. epidermidis. Studies in human L-cells and intestinal enteroids demonstrated that GspA alone is sufficient to enhance GLP-1 secretion. When administered in high-fat-fed mice, GspA-producing S. epidermidis significantly reduced markers associated with obesity and T2DM, including adiposity and hyperinsulinemia. Further characterization of GspA suggests a GLP-1 stimulatory action via calcium signaling. The presented results identify a novel host-microbe interaction which may ultimately lead to the development of a microbial peptide-based therapeutic for obesity and T2DM.\n\nImportanceThe human gastrointestinal microbiota has been shown to modulate metabolic disease, including Type II Diabetes Mellitus and obesity, through mechanisms involving gut hormone secretion. We initiated this study to identify bacterial strains that can stimulate one of these hormones, glucagon-like peptide-1. We first identified that some strains of Staphylococcus epidermidis have such stimulatory activity. We then found that these strains could be used in a mouse model of high-fat feeding to reduce markers associated with metabolic disease, including adiposity and elevated insulin levels. We also identified the peptide from S. epidermidis that stimulates glucagon-like peptide-1 and propose a mode of action through calcium signaling. This newly identified microbial-derived peptide and host-microbe interaction provide a promising therapeutic approach against Type II Diabetes Mellitus and obesity.

microbiology↗