Rho kinase isoforms in neurodegeneration: from cellular functions to therapeutic targets

Mitochondria serve as an important cellular organelle for maintaining neurotransmission and synaptic plasticity in neuronal cells by playing a key role in ATP generation, maintaining calcium homeostasis, and regulating the levels of reactive oxygen species (ROS), etc. The regulation of the dynamic nature of mitochondria, including their fission, fusion, and removal of damaged mitochondria by mitophagy, is also very important for neuronal health. Abnormalities in mitochondrial processes, including but not limited to fission, fusion, and mitophagy, are known to be associated with numerous neurodegenerative diseases (NDDs), such as Parkinson's disease (PD), Alzheimer's disease (AD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). In the recent past, the Rho kinase (ROCK) isoforms, particularly ROCK1 and ROCK2, have gained a lot of attention in NDDs, mainly for their role in regulating the dynamics of the mitochondria, mitophagy, and other cell signalling pathways. By adding phosphate groups to Drp1, ROCK1 is crucial in supporting excessive mitochondrial fission, causing the death of neuronal cells. On the other hand, ROCK2 inhibits Parkin-dependent mitophagy by inhibiting the PTEN protein, the activator of Parkin-dependent mitophagy. This impaired mitochondrial quality control via reduced mitophagic flux leads to oxidative stress and neuronal degeneration, the central pathological feature of NDDs. The inhibition of ROCK isoforms has shown great promise in neuroprotective effects, controlling the dynamics of mitochondria in neuronal cells, lowering inflammation, and improving motor and cognitive functions in preclinical models of different NDDs, indicating ROCK isoforms as an attractive therapeutic target in different NDDs. This review aims to highlight the therapeutic significance of targeting ROCK isoforms in different NDDs.