DRD3 (dopamine receptor D3) but not DRD2 activates autophagy through MTORC1 inhibition preserving protein synthesis
Creators: name: Barroso-Chinea, Pedro
name: Luis-Ravelo, Diego
name: Fumagallo-Reading, Felipe
name: Castro-Hernandez, Javier
name: Josmar Salas-Hernandez
name: Rodriguez-Nuñez, Julia
name: Febles-Casquero, Alejandro
name: Cruz-Muros, Ignacio
name: Afonso-Oramas, Domingo
name: Abreu-Gonzalez, Pedro
name: Moratalla, Rosario
name: Millan, Mark J.
name: Gonzalez-Hernandez, Tomas
Publisher: name: Taylor & Francis
Year: 2019
Subjects: subject: Biophysics
subject: Biochemistry
subject: 29999 Physical Sciences not elsewhere classified
subject: FOS: Physical sciences
subject: FOS: Physical sciences
subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Cell Biology
subject: Genetics
subject: Molecular Biology
subject: Physiology
subject: Pharmacology
subject: Biotechnology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: FOS: Chemical sciences
subject: Science Policy
subject: Immunology
subject: FOS: Clinical medicine
subject: FOS: Clinical medicine
subject: Developmental Biology
subject: Inorganic Chemistry
subject: Plant Biology

description: Growing evidence shows that autophagy is deficient in neurodegenerative and psychiatric diseases, and that its induction may have beneficial effects in these conditions. However, as autophagy shares signaling pathways with cell death and interferes with protein synthesis, prolonged use of autophagy inducers available nowadays is considered unwise. The search for novel autophagy inducers indicates that DRD2 (dopamine receptor 2)-DRD3 ligands may also activate autophagy, though critical aspects of the action mechanisms and effects of dopamine ligands on autophagy are still unknown. In order to shed light on this issue, <i>DRD2-</i> and <i>DRD3-</i>overexpressing cells and <i>drd2</i> KO, <i>drd3</i> KO and wild-type mice were treated with the DRD2-DRD3 agonist pramipexole. The results revealed that pramipexole induces autophagy through MTOR inhibition and a DRD3-dependent but DRD2-independent mechanism. DRD3 activated AMPK followed by inhibitory phosphorylation of RPTOR, MTORC1 and RPS6KB1 inhibition and ULK1 activation. Interestingly, despite RPS6KB1 inhibition, the activity of RPS6 was maintained through activation of the MAPK1/3-RPS6KA pathway, and the activity of MTORC1 kinase target EIF4EBP1 along with protein synthesis and cell viability, were also preserved. This pattern of autophagy through MTORC1 inhibition without suppression of protein synthesis, contrasts with that of direct allosteric and catalytic MTOR inhibitors and opens up new opportunities for G protein-coupled receptor ligands as autophagy inducers in the treatment of neurodegenerative and psychiatric diseases. AKT/Protein kinase B: thymoma viral proto-oncogene 1; AMPK: AMP-activated protein kinase; BECN1: beclin 1; EGFP: enhanced green fluorescent protein; EIF4EBP1/4E-BP1: eukaryotic translation initiation factor 4E binding protein 1; GPCR; G protein-coupled receptor; GFP: green fluorescent protein; HEK: human embryonic kidney; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MAP2K/MEK: mitogen-activated protein kinase kinase; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; MDA: malonildialdehyde; MTOR: mechanistic target of rapamycin kinase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; PPX: pramipexole; RPTOR/raptor: regulatory associated protein of MTOR, complex 1; RPS6: ribosomal protein S6; RPS6KA/p90S6K: ribosomal protein S6 kinase A; RPS6KB1/p70S6K: ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1; WT: wild type.