Secretagogin Binding Prevents α-Synuclein Fibrillation.

Secretagogin (SCGN) is a secreted calcium sensor that has emerged as a potential multifunctional protein of neuroendocrine cells. A significantly reduced level of expression of SCGN has been reported in the hippocampus of a mouse model of Alzheimer's disease (AD) and in Parkinson's patients, although the biochemical implications and mechanistic underpinnings of the altered SCGN expression in neurodegenerative diseases remain unknown. We have pursued the interaction of SCGN with α-synuclein that we discovered in impartial pull-down analyses to decode the SCGN interactome. SCGN physically binds α-synuclein and rescues it from detrimental fibrillation. Correspondingly, it is observed that a significant reduction in the cytotoxicity of α-synuclein fibrils is caused by SCGN. We map these antifibrillar attributes to the central region and C-terminal domain of SCGN, while the N-terminal domain is not essential for this activity. On the basis of these results, a broader neuroprotective function of SCGN by proficient chaperone action is proposed. An intriguing correlation of this interaction with a reduced level of expression of SCGN in neurodegenerative diseases shall inspire further studies of the physiological role of SCGN in precluding pathological protein aggregation.