Effects of a mutation in the Drosophila porin gene encoding mitochondrial voltage‐dependent anion channel protein on phototransduction

Abstract

Mitochondrial porins, also know as VDACs (voltage-dependent anion channels), play an important role in regulating energy metabolism, apoptosis, and the transport of metabolites across the mitochondrial outer membrane. So far three distinct isoforms of VDAC (VDAC1-3) have been reported in vertebrates, but their functions remain unknown. The annotation database of the Drosophila melanogaster genome sequence has identified four genes (porin, CG17137, CG17139, and CG17140) encoding different isoforms of VDACs. We identified post-translational modifications of PORIN that are specific to D. melanogaster eyes. We also identified the P-element insertion in the porin gene, porin(G2294), that is homozygous viable whereas all the porin mutants previously reported are homozygous lethal at the pupal stage. The mutant does not show any defects in fly morphology, survival, and photoreceptor structure. The mutant, however, produces <10% of the normal level of wild-type (WT) porin transcripts and 16.5% of WT level of the PORIN protein. The P-element insertion affects only the expression of Class I transcript but not Class II transcript of the porin gene. Unlike in WT, the mutant displays an ERG (electroretinogram) that is not maintained during a prolonged light stimulus. The revertant obtained from remobilization of the P-element in the mutant produces the WT level of porin transcripts and PORIN protein, and shows a normal ERG response. Our data suggest that the PORIN protein is important in maintaining a photoreceptor response during prolonged stimulation.

Drosophila Porin/VDAC Affects Mitochondrial Morphology

“…The homozygous porin mutants were viable and the adults seemed normal after eclosion, which is consistent with previous studies [14]. However, they started to show defects in their behaviors such as slow climbing ability against geotaxis and flying disability at the age of 20 days and then died within 30 days (Figure 1F, 1G, and Figure S1, respectively).…”

Voltage-Dependent Anion Channel 2 of Arabidopsis thaliana (AtVDAC2) Is Involved in ABA-Mediated Early Seedling Development

“…The time, location, and levels of gene transcripts are finely regulated in organisms, which ensure normal development and increased survival of plant under normal or stressful conditions. Thus, as an important element of mitochondrial in both plant and animal cells, the expression of VDAC affects the functions of mitochondria [22]. Overexpression of a rice VDAC in the Jurkat T-cell line has been shown to be capable of inducing mitochondrial-mediated apoptosis [6,23].…”

“…Those results indicate a tight correlation among VDAC gene expression level, protein expression level and channel activity [22,24,25]. As an isoform of VDAC gene family with a high degree of function conservation, AtVDAC2 might be inferred that it has the same change tendency as that of other VDAC isoforms.…”

Expressed sequence tags and proteomics of antennae from the tortricid moth, Epiphyas postvittana

“…Members of the VDAC family are involved in energy metabolism, apoptosis and the trafficking of small molecules and unfolded proteins across the mitochondrial/cytoplasm boundary. While no direct role for these proteins has been found in olfaction, VDACs have been implicated in vision, and in the ability to maintain photoreceptor response during prolonged periods of stimulation (Lee et al, 2007), suggesting they may perform a similar role in olfaction. Short chain dehydrogenases/reductases could potentially be involved in the metabolism of odorants in the antennae.…”