DISEASE-RELEVANT MUTANT VCP DYSREGULATES NF-κB ACTIVATION, AND ITS IMPACT ON THE EXPRESSION OF UBIQUITIN E3 LIGASES IN C2C12 MYOBLAST CELLS
Gema J Rodriguez, Julio C Flores, Carlos J Rodriguez-Ortiz, Masashi Kitazawa.
School of Natural Sciences, University of California, Merced, Merced, CA.
Inclusion body myopathy with Paget’s bone disease and frontotemporal dementia (IBMPFD) is an autosomal dominant disease caused by mutations on the valosin containing protein (VCP) gene. Over 80% of patients with VCP mutations develop progressive muscle weakness and wasting. Its underlying pathogenic mechanisms, however, remain largely unknown. Previously, we have shown that the disease-associated mutant VCP (R155H and A232E) prolongs NF-κB activation in C2C12 myoblast cells following an acute LPS stimulation. We hypothesize that the impaired resolution of NF-κB activation leads to aberrant transcriptional alterations, including up-regulation of inflammatory-related genes and muscle-specific ubiquitin ligases, which further promote degeneration of muscle cells. We first examined the changes in muscle-specific ubiquitin E3 ligases, Murf 1 and Atrogin 1, following the acute LPS exposure to C2C12 cells. Our preliminary immunofluorescence data indicates an increase in expression of Atrogin 1 protein levels, while no significant difference has been noticed in Murf 1 levels after NF-κB activation. To test whether VCP mutation exacerbates the expression of Atrogin1 and Murf 1 in comparison to wild-type VCP, we will transfect murine myoblast C2C12 cells with plasmid containing wild-type VCP, VCP-R155H or VCP-A232E. Transfected cells will then be incubated for 1 hour with 1 μg/mL LPS as NF-κB activator, followed by a 1 hour incubation for recovery without LPS. Protein levels will be quantified through western blot and intensity analysis of immunofluorescence staining. We expect greater protein levels of Atrogin1 and Murf1 in mutant VCP which may help to understand the underlying mechanisms of muscle degeneration in IBMPFD patients.