IGF-1 participates differently in regulation of severing activity of katanin and spastin.

Spastin and p60-katanin are AAA family proteins that participate in microtubule severing, while lipotransin, another AAA family protein is a hormone sensitive lipase interacting protein. Sequence alignment analysis suggests that lipotransin and human p60-katanin are the orthologs of each other. Studies identified that insulin may negatively regulate ATPase activity of lipotransin. To reveal the effects of insulin on regulation of severing activity of p60-katanin and spastin, hippocampal neurons over-expressing spastin and p60-katanin were treated with IGF-1. Changes in neuronal branching by considering the total process lengths and average process numbers were quantitatively analyzed. According to the results of this study, total process lengths of hippocampal neurons and average process numbers remained similar in control and p60-katanin over-expressing neurons upon IGF-1 treatment, while significant decrease was observed in spastin over-expressing neurons. This study indicated that IGF-1 participates differently in the regulation of spastin and p60-katanin in terms of neuronal branching.