ADrosophilaModel of Mutant Human Parkin-Induced Toxicity Demonstrates Selective Loss of Dopaminergic Neurons and Dependence on Cellular Dopamine

Abstract

Mutations in human parkin have been identified in familial Parkinson's disease and in some sporadic cases. Here, we report that expression of mutant but not wild-type human parkin in Drosophila causes age-dependent, selective degeneration of dopaminergic (DA) neurons accompanied by a progressive motor impairment. Overexpression or knockdown of the Drosophila vesicular monoamine transporter, which regulates cytosolic DA homeostasis, partially rescues or exacerbates, respectively, the degenerative phenotypes caused by mutant human parkin. These results support a model in which the vulnerability of DA neurons to parkin-induced neurotoxicity results from the interaction of mutant parkin with cytoplasmic dopamine.

Increased vesicular monoamine transporter enhances dopamine release and opposes Parkinson disease-related neurodegeneration in vivo

“…5). This enhanced transmitter release and locomotion suggest elevated dopamine neurotransmission in these mice, a finding reflected in previous work on the overexpression of the Drosophila vesicular monoamine transporter (DVMAT-A) (31)(32)(33). Together with previous findings demonstrating reduced dopamine release and locomotion in VMAT2-deficient animals, the results from the VMAT2-HI mice suggest that there is a gene dosage-dependent regulation of vesicular capacity and dopamine output (21,41,42).…”

“…Although the detrimental effects of reduced VMAT2 function are recognized, our understanding of the potential benefits of increased VMAT2 function in vivo has been limited to a Drosophila model (31)(32)(33). Thus, we generated VMAT2-overexpressing mice using a bacterial artificial chromosome (BAC) to determine whether increased vesicular packaging could provide an elevation of monoamine output in a mammalian system.…”

Drosophila Vesicular Monoamine Transporter Mutants Can Adapt to Reduced or Eliminated Vesicular Stores of Dopamine and Serotonin

“…We are using the model organism D. melanogaster to study how changes in VMAT activity and amine release may alter synaptic transmission and behavior (Chang et al 2006;Sang et al 2007). We have shown previously that the dVMAT gene contains two splice variants, dVMAT-A and -B and that overexpression of DVMAT-A protein has a dramatic effect on amine-dependent behaviors (Greer et al 2005;Chang et al 2006).…”

“…In response to the stimulus, wild-type flies will climb upward and against gravity (Connolly and Tully 1998). This assay has been used to test the performance of a variety of mutants and is notably sensitive to changes in dopaminergic signaling (Bainton et al 2000;Sang et al 2007). We first tested geotaxis under conditions in which most of the controls (w 1118 CS 10 : w À ; 1/1) were able to climb to an upper vial: 77% 6 4 of the control flies are able to reach the top vial in 15 sec ( Figure 9A).…”

Zinc supplement greatly improves the condition of parkin mutant Drosophila

“…Oxidative stress is considered to be a major factor in the pathogenesis of PD, as evidenced by an elevated content of redox-active iron and lipid peroxides in the diseased brain, impaired mitochondrial function, and alterations in the antioxidant defense mechanisms (Dexter et al, 1989;Jenner and Olanow, 1996;Greene et al, 2003;Pesah et al, 2004). Mutations in six genes, including parkin which encodes an E3 ubiquitin ligase, have been associated with rare, early-onset, familial forms of PD (West and Maidment, 2004;Gasser, 2005;Sang et al, 2007). Interestingly, some alleles of these genes might be susceptibility factors for environmental toxins (Choi et al, 2000;Warner and Schapira, 2003;Bueler, 2009).…”