Endocytotic Adaptor Protein HIP1R Required For Dendritic Development And Formation Of Excitatory Synapses In Cultured Hippocampal Neurons Of Rats

Huntington-interacting protein 1-related(HIP1R),a homologue of HIP1 and Sla2p,is an actin-binding protein,which binds to clathrin and inositol lipids via its putative central coiled-coil domain and epsin N-terminal homology(ENTH)domain,respectively.Similar to Sla2p,HIP1R also binds to F-actin through its COOH-terminal talin-like domain.Previous studies have suggested that HIP1R may play important roles in actin organization and endocytosis.However,little is known how HIP1R functions in the nervous system though it is highly expressed in the brain.In this study,we found that dendritic branching and complexity were reduced in cultured hippocampal neurons with shRNA knockdown of HIP1R.Moreover,synaptic density and spine morphology were also altered.The early endocytosis of EGFR was damaged and the phosphorylation of ERK was also decreased.Rescue and dominant negative experiments implied that the C terminal of HIP1R which contain Cortactin binding motif was critical for these dendritic development-related changes.PSD95 density and amplitude of mEPSC also decreased,suggesting that the number of excitatory synapses is decreased.Consistent with these results the total and surface expression levels of excitatory receptors were decreased.Interestingly,inhibitory receptors remain unchanged.Take together,these data indicates that HIP1R is required for dendritic development and excitatory synaptogenesis in cultured neurons.