Role of unconventional Myosin VI in localization and activity of DOCK7 in the brain
INTRODUCTION: Myosin VI (MVI) is a unique unconventional motor that moves toward the minus end of actin filaments. It is involved in endocytosis, cellular trafficking, cell migration and adhesion. The spontaneous mutation of a mouse Myo6 gene resulted in a characteristic circling phenotype (termed as Snell’s waltzer, SV) with sensorineural deafness and neurological symptoms accompanied by abnormalities in other organs. DOCK7 (dedicator of cytokinesis 7), a guanidine nucleotide exchange factor (GEF) for Rac1 and Cdc42 GTP that plays a role in axon formation and neuronal polarization, is a binding partner of MVI. We also characterized the MVI-DOCK7 interaction sites and showed that in PC12 cells the interaction was important for DOCK7 activity and NGF-stimulated protrusion formation. AIM(S): The main aim of this work is elucidation of the role of MVI in brain development and function. METHOD(S): Western-blot, confocal microscopy RESULTS: In hippocampus of WT brains, DOCK7 colocalized with MVI mainly in the perinuclear region. In the SV brains, DOCK7 distribution was more diffusive, not resembling the puncti‑like defined structures visible in the WT samples. Also, the absence of MVI affected DOCK7 activity asrevealed by estimation of the levels of phosphorylated (active) forms of DOCK7 and its downstream effector SAPK/JNK kinase. Moreover, a significantincrease ofthe levels of GFAP (glial fibrillary acidic protein) and caspase-3 were observed in the in hippocampus and cerebral cortex of SV brains. CONCLUSIONS: MVI is important both for DOCK7 distribution and activity, and that this interaction could play important role(s) in neuronal functions.