KLK6 and CAPN1 are partially co-localised with α-syn and regulate its level in human SH-SY5Y neuroblastoma cells. a Double-labelling immunofluorescence and confocal microscopy shows partial co-localisation of KLK6 and CAPN1 with α-syn. KLK6 (red) has a distinctive distribution pattern, along the plasma membrane, where it co-localises with some of the α-syn (top merged image and the magnified inset image). CAPN1 (green) has a widespread punctate cytosolic distribution and co-localises with α-syn within the cytoplasm (bottom merged image and in the magnified inset image). b-c siRNA-mediated knock-down of KLK6 or CAPN1 in SH-SY5Y cells overexpressing α-syn significantly increased endogenous α-syn level. The experiments were repeated in triplicate. The error bars represent the SEM. *P < 0.05 **P < 0.01.