title: Functional enhancement and protection of dopaminergic terminals by RAB3B overexpression.
abstract: In Parkinson's disease (PD), dopaminergic (DA) neurons in the substantia nigra (SN, A9) are particularly vulnerable, compared to adjacent DA neurons within the ventral tegmental area (VTA, A10). Here, we show that in rat and human, one RAB3 isoform, RAB3B, has higher expression levels in A10 compared to A9 neurons. RAB3 is a monomeric GTPase protein that is highly enriched in synaptic vesicles and is involved in synaptic vesicle trafficking and synaptic transmission, disturbances of which have been implicated in several neurodegenerative diseases, including PD. These findings prompted us to further investigate the biology and neuroprotective capacity of RAB3B both in vitro and in vivo. RAB3B overexpression in human dopaminergic BE (2)-M17 cells increased neurotransmitter content, [(3)H] dopamine uptake, and levels of presynaptic proteins. AAV-mediated RAB3B overexpression in A9 DA neurons of the rat SN increased striatal dopamine content, number and size of synaptic vesicles, and levels of the presynaptic proteins, confirming in vitro findings. Measurement of extracellular DOPAC, a dopamine metabolite, following l-DOPA injection supported a role for RAB3B in enhancing the dopamine storage capacity of synaptic terminals. RAB3B overexpression in BE (2)-M17 cells was protective against toxins that simulate aspects of PD in vitro, including an oxidative stressor 6-hydroxydopamine (6-OHDA) and a proteasome inhibitor MG-132. Furthermore, RAB3B overexpression in rat SN both protected A9 DA neurons and resulted in behavioral improvement in a 6-OHDA retrograde lesion model of PD. These results suggest that RAB3B improves dopamine handling and storage capacity at presynaptic terminals, and confers protection to vulnerable DA neurons.
authors.affiliation: Neuroregeneration Laboratories, Harvard Medical School, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA.
authors.forename: Chee Yeun
authors.initials: CY
authors.lastname: Chung
authors.forename: James B
authors.initials: JB
authors.lastname: Koprich
authors.forename: Penelope J
authors.initials: PJ
authors.lastname: Hallett
authors.forename: Ole
authors.initials: O
authors.lastname: Isacson
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D066298:In Vitro Techniques; D007976:Leupeptins / Q000633:toxicity; D007980:Levodopa / Q000494:pharmacology; D008959:Models, Neurological; D016627:Oxidopamine / Q000633:toxicity; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020734:Parkinsonian Disorders / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D017557:Ventral Tegmental Area / Q000378:metabolism; D020692:rab3 GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D007976:Leupeptins; D012333:RNA, Messenger; D015102:3,4-Dihydroxyphenylacetic Acid; D007980:Levodopa; D016627:Oxidopamine; C492131:RAB3B protein, human; C492132:Rab3b protein, rat; D020692:rab3 GTP-Binding Proteins; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D004298:Dopamine