Functional GPR37 trafficking protects against toxicity induced by 6-OHDA, MPP+ or rotenone in a catecholaminergic...

G protein-coupled receptor 37 (GPR37) is suggested to be implicated in the pathogenesis of Parkinson's disease and is accumulating in Lewy bodies within afflicted brain regions. Over-expressed GPR37 is prone to misfolding and aggregation, causing cell death via endoplasmic reticulum stress. Although the cytotoxicity of misfolded GPR37 is well established, effects of the functional receptor on cell viability are still unknown. An N2a cell line stably expressing green fluorescent protein (GFP)-tagged human GPR37 was created to study its trafficking and effects on cell viability upon challenge with the toxins 1-methyl-4-phenylpyridinium (MPP+), rotenone and 6-hydroxydopamine (6-OHDA). Neuronal-like differentiation into a tyrosine hydroxylase expressing phenotype, using dibutyryl-cAMP, induced trafficking of GPR37 to the plasma membrane. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability and lactate dehydrogenase (LDH) cell death assays revealed that GPR37 was protective against all three toxins in differentiated cells. In undifferentiated cells, the majority of GPR37 was cytoplasmic and the protective effects were more variable: GPR37 expression protected against rotenone and MPP+ but not against 6-OHDA in MTT assays, while it protected against 6-OHDA but not against MPP+ or rotenone in lactate dehydrogenase (LDH) assays. These results suggest that GPR37 functionally trafficked to the plasma membrane protects against toxicity.