Calsenilin is degraded by the ubiquitin–proteasome pathway

Calsenilin, a neuronal calcium binding protein that has been shown to have multiple functions in the cell, interacts with presenilin 1 (PS1) and presenilin 2 (PS2), represses gene transcription and binds to A-type voltage-gated potassium channels. In addition, increased levels of calsenilin are observed in the brains of Alzheimer’s disease and epilepsy patients. The present study was designed to investigate the molecular mechanism of calsenilin degradation pathways in cultured cells. Here, we demonstrate that inhibition of the ubiquitin–proteasomal pathway (UPP) but not lysosomal pathway markedly increased the expression levels of calsenilin. Immunofluorescence analysis revealed that following proteasomal inhibition calsenilin accumulated in the endoplasmic reticulum (ER) and Golgi, while lysosomal inhibition had no effect on calsenilin localization. In addition, we found the change of subcellular localization of PS1 from diffuse pattern to punctuate staining pattern in the ER and perinuclear region in the presence of calsenilin. These findings suggest that calsenilin degradation is primarily mediated by the UPP and that impairment in the UPP may contribute to the involvement of calsenilin in disease-associated neurodegeneration.

Research highlights► Calsenilin is an ubiquitinated protein whose degradation is mediated by the ubiquitin–proteasome pathway (UPP). ► Inhibition of the UPP delays the degradation of calsenilin and leads to an increase in the level of calsenilin. ► Inhibition of the proteasomal pathway results in the accumulation of calsenilin in the ER and Golgi. ► The Subcellular localization of PS1 changes from a diffuse to a punctuate staining pattern in the ER and perinuclear region in the presence of calsenilin. ► These findings suggest that impairment in the UPP may contribute to the involvement of calsenilin in disease-associated neurodegeneration.