Mechanisms of contractile dysfunction in the obstructed bladder: Role of desmin and vimentin

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Abstract Lower urinary tract dysfunction (LUTD) is a common disease whose incidence and prevalence increase as the population ages and the the current therapeutic approaches are ineffective. LUTD is strongly associated with bladder smooth muscle (BSM) hypertrophy secondary to benign prostatic hyperplasia (BPH)-induced partial bladder outlet obstruction (PBOO). The molecular pathogenesis of BPH and BSM dysfunction is poorly understood; filling this gap in our knowledge will likely lead to the identification of new therapeutic targets and more effective LUTD drugs or management strategies. We and others have demonstrated that the contractile dysfunction, increased mitochondrial ROS and reduced ATP levels of BSM in the obstructed bladder is associated with the overexpression of the intermediate filament (IF) proteins desmin and vimentin. Previous studies as well as preliminary data presented herein suggest JNK2 as a major effector of the BSM contractile dysfunction induced by the overexpression of desmin and vimentin and demonstrate that an IFs/JNK2- dependent mechanism contributes to the contractile dysfunction in bladder outlet obstruction. In the current proposal we have identified via microarray significant induction of the mitochondrial protein G0S2 in human and murine BSM strips and cells overexpressing desmin and vimentin. Our additional preliminary data further demonstrate that inhibition of G0S2 expression decreases phospho-JNK levels, increases mitochondrial ATP, and decreases the ROS production in desmin- and vimentin- overexpressing murine and human BSM strips and cells. Further, we demonstrate the interaction of G0S2 with voltage-dependent anion channel (VDAC). VDAC promotes ATP/ADP exchange across the mitochondrial outer membrane in association with adenine nucleotide translocase and mitochondrial creatine kinase. G0S2 binding to VDAC presumably disrupts the ATP/ADP exchange thereby, reducing the mitochondrial ATP level and increasing the mitochondrial ROS production. We hypothesize that mitochondrial G0S2 mediates desmin- and vimentin-induced BSM contractile dysfunction via phospho-JNK2. We further hypothesize that G0S2 interaction with the VDAC promotes the mitochondrial ROS production and the ROS-induced phospho-JNK2 contributes to the contractile dysfunction. Three Specific Aims are designed to address these hypotheses. In Aim 1, we will establish the role of mitochondrial G0S2 in IF protein overexpression-induced BSM contractile dysfunction. In Aim 2 we will determine whether IF protein overexpression-induced BSM contractile dysfunction is due to G0S2 and VDAC interaction. In Aim 3 we will employ in vivo models to establish the role of G0S2 and JNK2 in murine PBOO induced BSM contractile dysfunction: We expect our studies to delineate a mechanism of contractile dysfunction mediated by G0S2 and thus identify therapeutic targets for the treatment of PBOO/LUTD.