Autoantibodies against Muscarinic Type 3 Receptor in Sjögrens Syndrome Inhibit Aquaporin 5 TraffickingReportar como inadecuado

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Sjögren-s syndrome SjS is a chronic autoimmune disease that mainly targets the salivary and lacrimal glands. It has been controversial whether anti-muscarinic type 3 receptor α-M3R autoantibodies in patients with SjS inhibit intracellular trafficking of aquaporin-5 AQP5, water transport protein, leading to secretory dysfunction. To address this issue, GFP-tagged human AQP5 was overexpressed in human salivary gland cells HSG-hAQP5 and monitored AQP5 trafficking to the plasma membrane following carbachol CCh, M3R agonist stimulation. AQP5 trafficking was indeed mediated by M3R stimulation, shown in partial blockage of trafficking by M3R-antagonist 4-DAMP. HSG-hAQP5 pre-incubated with SjS plasma for 24 hours significantly reduced AQP5 trafficking with CCh, compared with HSG-hAQP5 pre-incubated with healthy control HC plasma. This inhibition was confirmed by monoclonal α-M3R antibody and pre-absorbed plasma. Interestingly, HSG-hAQP5 pre-incubated with SjS plasma showed no change in cell volume, compared to the cells incubated with HC plasma showing shrinkage by twenty percent after CCh-stimulation. Our findings clearly indicate that binding of anti-M3R autoantibodies to the receptor, which was verified by immunoprecipitation, suppresses AQP5 trafficking to the membrane and contribute to impaired fluid secretion in SjS. Our current study urges further investigations of clinical associations between SjS symptoms, such as degree of secretory dysfunction, cognitive impairment, and-or bladder irritation, and different profiles titers, isotypes, and-or specificity of anti-M3R autoantibodies in individuals with SjS.

Autor: Byung Ha Lee, Adrienne E. Gauna, Geidys Perez, Yun-jong Park, Kaleb M. Pauley, Toshihisa Kawai, Seunghee Cha



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