Possible interactors of alsin and effects of its expression on four motor neuron disease-related proteins

Abstract

Motor neuron disorders, characterized by selective motor neuron degeneration, consist of a large group of diseases with overlapping genes and common pathological mechanisms. Mutations in ALS2, associated with three types of motor neuron disorders with early age of onset, result in a loss of function of the protein, suggesting a crucial role of the protein product, alsin, in motor neuron integrity. However, the exact function of alsin is not known yet. This study aims to gain insights into alsin’s function by investigating its relations both at mRNA and protein levels with proteins that are involved in different motor neuron disorders. Spastin (Spg4) and spartin (Spg20), selected as representative genes, are involved in upper motor neuron disorders, while heat shock protein B1 (HspB1) and heat shock protein B8 (HspB8) were selected due to their associations with lower motor neuron disorders. Since ALS2 mutations result in a loss of function, an Als2 knock-down stable cell line was generated. Q-RT PCR revealed statistically significant alterations in the expression levels of Sgp20, Spg4, HspB1 and HspB8 in this cell line, as compared to the control cell line. For the first time in literature, the inhibitory effect of Als2 on HspB1 expression under heat shock conditions implicated a possible role of alsin in heat shock response. At the protein level, it was observed that spartin and alsin were colocalized in the perinuclear region of differentiated neuronal N2a cells. Furthermore, immunoprecipitation studies revealed the co-precipitation of these proteins in the same protein complex, indicating a possible physical interaction. We hope that this thesis, the first study, showing relations of alsin with spartin and HspB1, will contribute to this unexplored field.