Role of cerebral dopamine neurotrophic factor in endoplasmic reticulum stress

Abstract

The cerebral dopamine neurotrophic factor (CDNF) is a peptide of 187 amino acids located in the endoplasmic reticulum of numerous cell types and evolutionarily conserved. CDNF exerts a protective effect on neurons in cellular and animal models of various neurodegenerative diseases, but the molecular mechanism of this effect is unknown. Many neurodegenerative diseases are associated with the deregulation of proteostasis in the endoplasmic reticulum. Deregulation of proteostasis produces reticular stress, which initially triggers the response to misfolded proteins and, if stress persists over time, signaling pathways related to cell death or apoptosis are induced. Several studies have revealed that an adaptive response resolves the endoplasmic reticulum stress by attenuating protein synthesis, inducing the expression of chaperones, and metabolizing misfolded proteins. In this thesis, it was investigated whether CDNF regulates proteostasis of the endoplasmic reticulum. To this end, the function of CDNF was determined in an endoplasmic reticulum stress model induced by Thapsigargin, in HEK293-T cells and hippocampal neurons in culture. It was observed that the induced expression of CDNF significantly increased the viability of HEK293-T cells exposed to Thapsigargin. This effect correlated with the increase in protective protein levels of the early misfolded protein response such as BiP, ATF4, ATF6, and XBP-1, both in HEK293-T cells and in neurons. Also, the induced-expression of CDNF reduced the levels of pro-apoptotic proteins CHOP and active caspase-3. It was determined that CDNF protects cells from the endoplasmic reticulum, since a mutant version of CDNF, lacking the endoplasmic reticulum retention sequence, and therefore secreted, did not protect the cells against stress-induced by Thapsigargin. In conclusion, CDNF regulates proteostasis in the endoplasmic reticulum by inducing the response to adaptive misfolded protein and inhibiting pro-apoptotic pathways activated by endoplasmic reticulum stress. Finally, in the last part of this thesis, a molecular device for the regulated expression of CDNF that combines optogenetic methods with a lentiviral platform was designed and constructed.