In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Indirect immunofluorescence labeling of normal rat kidney (NRK) cells with antibodies recognizing a lysosomal glycoprotein (LGP 120; Lewis, V., S.A. Green, M. Marsh, P. Vihko, A. Helenius, and I. Mellman, 1985, J. Cell Biol., 100:1839-1847) reveals that lysosomes accumulate in the region around the microtubule-organizing center (MTOC). This clustering of lysosomes depends on microtubules. When the interphase microtubules are depolymerized by treatment of the cells with nocodazole or during mitosis, the lysosomes disperse throughout the cytoplasm. Lysosomes recluster rapidly (within 30-60 min) in the region of the centrosomes either upon removal of the drug, or, in telophase, when repolymerization of interphase microtubules has occurred. During this translocation process the lysosomes can be found aligned along centrosomal microtubules. Endosomes and lysosomes can be visualized by incubating living cells with acridine orange. We have analyzed the movement of these labeled endocytic organelles in vivo by video-enhanced fluorescence microscopy. Translocation of endosomes and lysosomes occurs along linear tracks (up to 10 microns long) by discontinuous saltations (with velocities of up to 2.5 microns/s). Organelles move bidirectionally with respect to the MTOC. This movement ceases when microtubules are depolymerized by treatment of the cells with nocodazole. After nocodazole washout and microtubule repolymerization, the translocation and reclustering of fluorescent organelles predominantly occurs in a unidirectional manner towards the area of the MTOC. Organelle movement remains unaffected when cells are treated with cytochalasin D, or when the collapse of intermediate filaments is induced by microinjected monoclonal antivimentin antibodies. It can be concluded that translocation of endosomes and lysosomes occurs along microtubules and is independent of the intermediate filament and microfilament networks.

The orphan G protein-coupled receptor 37 (GPR37) is a substrate of parkin; its insoluble aggregates accumulate in brain samples of Parkinson's disease patients. We report here that GPR37 interacts with the dopamine transporter (DAT) and modulates DAT activity. GPR37 and DAT were found colocalized in mouse striatal presynaptic membranes and in transfected cells and their interaction was confirmed by coimmunoprecipitation assays. Gpr37-null mutant mice showed enhanced DAT-mediated dopamine uptake in striatal membrane samples, with a significant increase in the number of plasma membrane DAT molecules. The null mutant mice also exhibited a decrease in cocaine-induced locomotor activity and in catalepsy induced by dopamine receptor antagonists. These results reveal the specific role of GPR37, a putative peptidergic G proteincoupled receptor, in modulating the functional expression of DAT and the behavioral responses to dopaminergic drugs.G protein-coupled receptor ͉ Parkinson's disease ͉ dopamine transporter T he orphan G protein-coupled receptor 37 (GPR37) is homologous to endothelin (ET B -R) and bombesin (GRP-R, NMB-R) receptors (1) and it is highly expressed in mammalian brain oligodendrocytes, Purkinje cells, and neurons belonging to the CA3 hippocampal region and to the substantia nigra (SN) pars compacta (2). GPR37 is a substrate of the ubiquitin-protein ligase parkin, and it has been named parkin-associated endothelin-like receptor (PAEL-R) (3). An insoluble form of GPR37 is accumulated in brain samples of Parkinson's disease (PD) patients, and the overexpression of GPR37 in cell cultures, in the absence of parkin, can lead to unfolded protein-induced cell death (3, 4). Little is known about the physiological function of the receptor in the brain and in dopaminergic neurons in particular, although it has been speculated that the aggregation of GPR37 in insoluble complexes is responsible for the preferential loss of SN neurons through the endoplasmic reticulum-specific apoptotic pathway (5, 6). Recent data reported an interaction between GPR37, the head activator neuropeptide and its binding protein (sorting protein-related receptor; SorLA), supporting the hypothesis that GPR37 is involved in neuronal cell survival (7). To investigate the receptor's function, we generated homozygous Gpr37-null mutant mice, which exhibit a reduction in striatal dopamine (DA) content, specific locomotor deficits, and enhanced sensitivity to amphetamine (8).Several binding partners for the DA transporter (DAT) have been identified, suggesting that a regulated multiprotein complex controls its synthesis, targeting, and expression at specific cellular membrane domains (9). Presynaptic DAT expression is of crucial importance in modulating the synaptic availability of DA at nigrostriatal synapses, and its regulation is dynamically controlled for the maintenance of normal dopaminergic neurotransmission. The increase or decrease of DAT expression in the presynaptic membranes results in decreased or increased synaptic DA concentration, ...

GPR37 is an orphan G protein-coupled receptor expressed in mammalian brain, and its insoluble aggregates are found in the brain samples of juvenile Parkinson's disease patients. We have produced a Gpr37 knock-out mouse strain and identified several phenotypic features that are similar to those reported for mutants of genes encoding components of synaptic dopamine vesicles. Our results reveal an unanticipated role of GPR37 in regulating substantia nigra-striatum dopaminergic signaling. Gpr37 ؊/؊ mice are viable, with normal brain development and anatomy, but they exhibit reduced striatal dopamine content, enhanced amphetamine sensitivity, and specific deficits in motor behavior paradigms sensitive to nigrostriatal dysfunction. These functional alterations are not associated with any substantial loss of substantia nigra neurons or degeneration of striatal dopaminergic afferences, the main histological marks of Parkinson's disease. The inactivation of GPR37, in fact, has protective effects on substantia nigra neurons, causing resistance to treatment with the Parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

In the developing cerebellum, the proliferation and differentiation of glial and neuronal cell types depend on the modulation of the sonic hedgehog (Shh) signaling pathway. The vertebrate Gprotein-coupled receptor 37-like 1 (GPR37L1) gene encodes a putative G-protein-coupled receptor that is expressed in newborn and adult cerebellar Bergmann glia astrocytes. This study shows that the ablation of the murine Gpr37l1 gene results in premature down-regulation of proliferation of granule neuron precursors and precocious maturation of Bergmann glia and Purkinje neurons. These alterations are accompanied by improved adult motor learning and coordination. Gpr37l1 −/− mice also exhibit specific modifications of the Shh signaling cascade. Specific assays show that in Bergmann glia cells Gpr37l1 is associated with primary cilium membranes and it specifically interacts and colocalizes with the Shh primary receptor, patched 1. These findings indicate that the patched 1-associated Gpr37l1 receptor participates in the regulation of postnatal cerebellum development by modulating the Shh pathway.mutant mouse model | mitogenic signaling