For example, fast-fatigable muscle fibers, the first ones denervated in the SOD1 mouse model, are innervated by the most phasic subtype of MNs. Hyperexcitability and evidence of ER stress is detected specifically in MNs innervating fast-fatigable muscles prior to initial denervation further suggesting that these events serve as stressors that continue until the neuron reaches a threshold that jeopardizes its survival (Saxena and Caroni 2011). Nonetheless, many of the events associated with cellular stress often represent a protective Inhibitors,research,lifescience,medical response by the cell
and therefore do not precipitate neuronal dysfunction, but rather prevent or delay the process (reviewed in Robinson et al. 2011; Gould and Milligan 2012). Axonal deficits in ALS The events discussed above can lead to Inhibitors,research,lifescience,medical impairment of fast and slow axonal transport in vivo that has been well established in adult SOD1 mutant mice (Collard et al. 1995; Zhang et al. 1997; Warita et al. 1999; Williamson and Cleveland 1999; Sasaki et al. 2004; Ligon et al. 2005) and in human ALS patients (Bradley et al. 1983) deficits have even been reported in cultured embryonic MNs from SOD1
mice (Kieran et al. 2005; De Vos et al. 2007). Although the transport deficits in adult SOD1 mutant mice occur prior to disease onset, www.selleckchem.com/products/AZD6244.html whether they occur before the onset Inhibitors,research,lifescience,medical of muscle denervation and thus represent a primary event or are secondary to axon/synapse loss or dysfunction is not known. The impairment of axonal transport in SOD1 mice has been attributed to appearance of neurofilament Inhibitors,research,lifescience,medical (NF) inclusions in mutant axons (Zhang et al. 1997), but mutations in transport proteins in the dynein/dynactin complex also occur (LaMonte et al. 2002; Hafezparast
et al. 2003; Puls et al. 2003). The enrichment within neurons of mitochondria near sites of activity such as axons, dendrites, and presynaptic terminals Inhibitors,research,lifescience,medical indicates that mitochondrial localization may be the target of disease toxicity in fALS as well as in other neurodegenerative diseases very involving distal-to-proximal axonal pathology (Gould and Oppenheim 2007). It is an attractive possibility that altered transport of either normal or defective mitochondria to and/or from MN presynaptic terminals contributes to neuromuscular denervation and MN disease (but see, Marinkovic et al. 2012). Mitochondrial pathology is prominent in ALS Alterations in mitochondria morphology and function have been identified in both animal models and ALS patient material and have been proposed to contribute to disease pathology and progression (Schon and Przedborski 2011). Dysfunction in mitochondrial Ca+2 buffering, bioenergetics, fission, fusion, and transport occur in animal models of the disease (reviewed in Cozzolino et al.