Cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte derived neurotrophic factor (MANF) form an evolutionary conserved protein family with cytoprotective activities in neurons and other cell types . CDNF was originally identified and characterized by our group [2, 3] and is homologous to mammalian MANF protein . A single homologous gene for mammalian MANF/CDNF is also found in invertebrate animals, such as D. melanogaster  and C. elegans, in which no other neurotrophic factors have been identified so far.
In cells, MANF and CDNF localize to the endoplasmic reticulum (ER) which is an important site for protein synthesis, folding, modification, and transport. Different cellular insults, including exposure to toxins or lack of oxygen, can disturb the normal ER function leading to the accumulation of misfolded proteins, a condition referred as ER stress. Importantly, ER stress and unfolded protein response (UPR) signaling is activated in pancreatic islets of MANF knockout mice, which develop diabetes .
We are studying the molecular mechanism of action and cellular binding partners of CDNF and MANF proteins in order to understand their neuroprotective and cytoprotective functions in more detail. To do this we use biochemical, molecular and cell biology methods. We are particularly interested in MANF/CDNF interactions taking place in the ER, and roles of MANF and CDNF in the regulation of UPR signaling pathway.
We have resolved the three-dimensional structure of MANF/CDNF proteins by X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy [7, 8]. The unique 3D structure of MANF/CDNF proteins consists of two domains, an amino-terminal saposin-like domain and a carboxy-terminal SAP-domain. We are using the 3D structure model to try to predict and understand how CDNF/MANF proteins interact with other proteins. We have identified regions in the amino-acid sequence of MANF, which are important for its neuroprotective activity . We recently demonstrated that MANF directly interacts with an UPR sensor protein IRE1 and regulates its activity thus promoting ER homeostasis and cell survival . We also showed that the survival promoting activity of MANF in primary neurons is dependent on UPR pathways. Using a proteomic approach, we have identified several MANF interacting proteins . We have also characterized the levels of endogenous MANF and CDNF proteins in human neurodegenerative and other diseases using in-lab developed immunoassays . Abnormal CDNF/MANF expression levels could reveal pathological conditions in humans.
Galli, E., et al., Increased Serum Levels of Mesencephalic Astrocyte-Derived Neurotrophic Factor in Subjects With Parkinson's Disease. Front Neurosci, 2019. 13: p. 929. 10.3389/fnins.2019.00929