a b s t r a c tGlial cell line-derived neurotrophic factor (GDNF) and its canonical receptor Ret can signal together or independently to fulfill many important functions in the midbrain dopaminergic (DA) system. While Ret signaling clearly impacts on the development, maintenance and regeneration of the mesostriatal DA system, the physiological functions of GDNF for the DA system are still unclear. Nevertheless, GDNF is still considered to be an excellent candidate to protect and/or regenerate http://dx.doi.org/10.1016/j.febslet.2015.11.006 0014-5793/Ó 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.Abbreviations: 6-OHDA, 6-hydroxy-dopamine; Akt, PKB, protein kinase B, serine/threonine-specific protein kinase; BDNF, brain derived neurotrophic factor; CaMKIIb, calcium-calmodulin-dependent protein kinase II b isoform; cAMP, 3 0 ,5 0 -cyclic adenosine monophosphate; catecholamine, monoamine, neurotransmitter type including dopamine, epinephrine (adrenaline) and norepinephrine (noradrenaline); CCCP, carbonyl cyanide m-chlorophenyl hydrazone; Cdc42, cell division control protein 42 homolog, a plasma membrane-associated small GTPase of the Rho family; COMT, catechol-O-methyltransferase; CoREST, co-repressor for element-1-silencing transcription factor, a chromatin-modifying corepressor complex that acts with REST (repressor for element-1 silencing transcription factor) complex; GABA, c-aminobutyric acid, inhibitory neurotransmitter in mammalian central nervous system; GTPase, cycles between an active GTP-bound and an inactive GDP-bound state; DA, dopaminergic; DAT, dopamine transporter; DJ-1, deglycase, oxidative stress sensor and redox-sensitive chaperone and protease; DOK1/4/5/6, docking proteins, have a PH and SH3 domain; EGFP, enhanced green fluorescent protein; EGR1, early growth response protein 1, Zif268 (zinc finger protein 225), NGFI-A (nerve growth factor-induced protein A), is a zinc finger transcription factor; Enigma, adaptor protein of the PDZ-LIM family; ER, endoplasmatic reticulum; ERK, extracellular-signal-regulated kinases, classical MAPKs; FosB/DFosB, FBJ murine osteosarcoma viral oncogene homolog B, a transcription factor with a truncated D form; FRS2, fibroblast growth factor receptor substrate 2, adaptor protein; GAP1/2, GTPase-activating proteins 1 and 2; GDNF, glia cell line-derived neurotrophic factor; GFLs, GDNF family of ligands; GFRa, GDNF family receptor a; GPI, glycosylphosphatidylinositol; GRB2/7/10, growth factor receptor-bound protein 2, 7 and 10, adaptor proteins; gsk3b, glycogen synthase kinase 3b; HIF-1a, hypoxia-inducible factor-1alpha; IRS1/2, insulin receptor substrate 1, adaptor protein, contains a PTB and PH domain; JNK, c-Jun N-terminal kinases, members of the MAPK family of proteins; Kv4.3 and KChip3, subunits of the Ca 2+ -sensitive, voltage gated A-type K+ channel; LIM, (acronym combining the first letters of three proteins -Lin11, Isl-1 and Mec-3 -that have this common domain) protein interaction domain of two contiguous zin...