Background: Altered expression of vacuole membrane protein 1 (VMP1) has recently been observed in the context of multiple sclerosis and Parkinson's disease (PD). However, how changes in VMP1 expression may impact pathogenesis has not been explored.
Objective: This study aimed to characterize how altered VMP1 expression affects NLRP3 inflammasome activation and mitochondrial function.
Methods: VMP1 expression was depleted in a monocytic cell line using CRISPR-Cas9. The effect of VMP1 on NLRP3 inflammasome activation was examined by stimulating cells with LPS and ATP or α-synuclein fibrils. Inflammasome activation was determined by caspase-1 activation using both a FLICA assay and a biosensor as well as by the release of proinflammatory molecules measured by ELISA. RNA-sequencing was utilized to define global gene expression changes resulting from VMP1 deletion. SERCA activity and mitochondrial function were investigated using various fluorescence microscopy-based approaches including a novel method that assesses the function of individual mitochondria in a cell.
Results: Here, we report that genetic deletion of VMP1 from a monocytic cell line resulted in increased NLRP3 inflammasome activation and release of proinflammatory molecules. Examination of the VMP1-dependent changes in these cells revealed that VMP1 deficiency led to decreased SERCA activity and increased intracellular [Ca2+]. We also observed calcium overload in mitochondria in VMP1 depleted cells, which was associated with mitochondrial dysfunction and release of mitochondrial DNA into the cytoplasm and the extracellular environment.
Conclusions: Collectively, these studies reveal VMP1 as a negative regulator of inflammatory responses, and we postulate that decreased expression of VMP1 can aggravate the inflammatory sequelae associated with neurodegenerative diseases like PD.
Keywords: Autophagy; Dysfunctional mitochondria; Inflammasome; NLRP3; SERCA; VMP1; α-Synuclein.
© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.