Abstract
Oxidative stress-induced neuronal apoptosis plays an important role in the progression of central nervous system (CNS) diseases. In our study, when neuronal cells were exposed to hydrogen peroxide (H2O2), an exogenous oxidant, cell apoptosis was observed with typical morphological changes including membrane blebbing, neurite retraction and cell contraction. The actomyosin system is considered to be responsible for the morphological changes, but how exactly it regulates oxidative stress-induced neuronal apoptosis and the distinctive functions of different myosin II isoforms remain unclear. We demonstrate that myosin IIA was required for neuronal contraction, while myosin IIB was required for neuronal outgrowth in normal conditions. During H2O2-induced neuronal apoptosis, myosin IIA, rather than IIB, interacted with actin filaments to generate contractile forces that lead to morphological changes. Moreover, myosin IIA knockout using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9) reduced H2O2-induced neuronal apoptosis and the associated morphological changes. We further demonstrate that caspase-3/Rho-associated kinase 1 (ROCK1) dependent phosphorylation of myosin light chain (MLC) was required for the formation of the myosin IIA-actin complex. Meanwhile, either inhibition of myosin II ATPase with blebbistatin or knockdown of myosin IIA with siRNA reversely attenuated caspase-3 activation, suggesting a positive feedback loop during oxidative stress-induced apoptosis. Based on our observation, myosin IIA-actin complex contributes to actomyosin contractility and is associated with the positive feedback loop of caspase-3/ROCK1/MLC pathway. This study unravels the biochemical and mechanistic mechanisms during oxidative stress-induced neuronal apoptosis and may be applicable for the development of therapies for CNS diseases.
Highlights
Oxidative stress-induced neuronal apoptosis has been implicated in many central nervous system (CNS) diseases, including Alzheimer’s diseases, stroke and schizophrenia (Hayashi-Takagi et al, 2014; Volpe and Paneni, 2015; Kamat et al, 2016)
Similar results were observed in neurons (Figure 10). These findings demonstrated that caspase3/ROCK1/myosin light chains (MLC) activation plays a key role in triggering the downstream myosin IIA-actin hyperactivation upon hydrogen peroxide (H2O2) exposure
Myosin IIA was dispersed throughout the cytoplasm, in contrast to the pronounced peripheral localization of myosin IIB and F-actin, which indicated that myosin IIA was better suited for large scale contractile processes than myosin IIB (Wylie and Chantler, 2003)
Summary
Oxidative stress-induced neuronal apoptosis has been implicated in many central nervous system (CNS) diseases, including Alzheimer’s diseases, stroke and schizophrenia (Hayashi-Takagi et al, 2014; Volpe and Paneni, 2015; Kamat et al, 2016). It has been demonstrated that the actomyosin system is responsible for the structural and morphological changes during the execution of apoptosis, such as dynamic cell contraction, membrane blebbing and chromatin condensation (Croft et al, 2005; Even-Ram et al, 2007; Ndozangue-Touriguine et al, 2008). In the CNS, myosin II has been demonstrated to regulate neuronal morphogenesis (Ozkan et al, 2015), migration (Solecki et al, 2009), axon outgrowth (Pool et al, 2011), as well as growth cone motility (Medeiros et al, 2006). How exactly the actomyosin system regulates oxidative stress-induced neuronal apoptosis remains unclear
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