Poster Presentation Melbourne Protein Group Student Symposium 2013

 The relationship between ER-Golgi transport and axonal transport – the implications in the pathogenesis of Amyotrophic Lateral Sclerosis (ALS) (#74)

Brooke Smith 1 , Kai Ying Soo 1 , Vy Hoang 1 , Vinod Sundaramoorthy 1 , Julie Atkin 1
  1. Latrobe University, Bundoora, VIC, Australia

 Amyotrophic Lateral Sclerosis (ALS) is an adult-onset rapidly progressive neurodegenerative disease targeting the both upper and lower motor neurons of the brainstem, cortex and spinal cord.1  The formation of intracellular Cu,Zn superoxide dismutase-1 (SOD1) aggregates, are a prominent pathological hallmark in ALS with SOD1 mutations causing familial form of ALS.1  Despite extensive research in ALS, the cellular mechanisms initiating neurodegeneration remain unclear.9  Several mechanisms are implicated in ALS, including endoplasmic reticulum (ER) stress2  and axonal transport defects.3  Axons of motor neurons can extend up to one metre thus are uniquely vulnerable due to a high dependence on an efficient and robust intracellular transport system.4  Axonal transport is essential for long-distance signalling and the supply and clearance of proteins, RNA and organelles within the motor neuron6  and disruptions to axonal transport are seen in many neurodegenerative diseases.5  The ER extends along the axon in neurons7  and Golgi outposts are found in dendrites.8  However little is known about whether ER-Golgi transport and axonal transport is interrelated and investigating this link is the objective of this study. We have shown that ER-Golgi transport is inhibited by mutant SOD1 in neuronal cells. SOD1-EGFP vectors were co-transfected with a VSVG-mCherry construct and ER-Golgi transport was quantified using Manders coefficient. Mutant SOD1 inhibited VSVG transport in differentiated human neuroblastoma SHSY5Y cells. However, this inhibition can be rescued by overexpression of Sar1, which is an essential and rate limiting component of the coat protein complex II (COPII), which facilitates vesicular export from the ER to Golgi.7  Using immunofluorescence and confocal microscopy, we also found that the proteins facilitating ER-Golgi transport are present in the axon of SHSY-5Y cells. This finding suggests that ER-Golgi transport and axonal transport might be linked. In conclusion, we have shown that mutant SOD1 inhibits ER-Golgi transport as well as axonal transport in ALS. Overexpression of Sar1 can rescue ER-Golgi transport, however its role in axonal transport still needs to be clarified. 

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