GLCE regulates PC12 cell neuritogenesis induced by nerve growth factor through activating SMAD/ID3 signalling

Neurodevelopment is orchestrated by a series of growth factor-HS (heparan sulfate) interactions which are involved in neuritogenesis. GLCE (glucuronic acid epimerase) is a critical enzyme involved in HS synthesis, which converts GlcA (D-glucuronic acid) into IdoA (L-iduronic acid). However, the function of GLCE in neuritogenesis is largely unknown. In the present study we showed that GLCE depletion caused arrested PC12 cell growth and promoted the cell neuritogenesis and differentiation induced by NGF (nerve growth factor). PC12 cell growth was boosted by overexpression of GLCE, and neuritogenesis was impaired when GLCE depletion was rescued. Interestingly, overexpression of wild-type GLCE with Y168A and Y222A mutations led to enhanced PC12 cell growth and attenuated the neuritogenesis triggered by GLCE silencing. We showed further that GLCE depletion blocked SMAD1/5/8 phosphorylation; however, this signalling could be restored by GLCE or the mutation of its active enzymatic site. In addition, the downstream effector of SMAD1/5/8, ID3 (inhibitor of DNA binding/differentiation 3) was induced by GLCE. ID3 silencing inhibited PC12 cell growth and induced cell neuritogenesis and differentiation. In addition, ectopic expression of ID3 partially rescued the phenotype caused by GLCE silencing. The results of the present study suggest that GLCE plays a key role in PC12 cell growth and neuritogenesis through SMAD/ID3 signalling.