An Arabidopsis Kinesin AtKP1 Is Involved In Regulation Of Mitochondrial Ninctions Via Its Interaction With Mitochondrial AtVDAC3

Mitochondria, where aerobic respiration and ATP synthesis take place, are essential organelles in eukaryotes. A number of studies have shown that cytoskeleton and its associated proteins interact with mitochondria and thus regulate mitochondrial functions. It is recently demonstrated that cytoskeleton could interact with voltage-dependent anion channels (VDACs), which regulate mitochondrial respiration and the permeability of ADP through mitochondrial outer membrane. However, investigation of the underlying mechanism in plant cells is limited. We have previously identified a plant-specific microtubule-associated kinesin AtKP1 localized on mitochondria and specifically interacted with AtVDAC3 via its C-terminal 200 amino acids (C200).Both AtKPl and AtVDAC3 have been proved to be involved in seed germination at low temperature. Further investigating into the interaction between AtKP1 and AtVDAC3 and their effects on mitochondrial functions has scientific significance in revealing its regulatory mechanism on plant mitochondrial respiration at low temperature, as well as the relationship of cytoskeleton-associated protein and mitochondrial functions in plants.To investigate the effect of AtKP1 and its interaction with AtVDAC3 on mitochondrial functions, and to elucidate mitochondrial mechanism on seed germination at low temperature, further exploration on mitochondrial functions were assessed. Measurements of oxygen consumption showed that AtKP1 and AtVDAC3 were involved in maintaining aerobic respiration balance. atkpl and atvdac3 mutants exhibited higher oxygen consumption, of which the cytochrome pathway increased while the alternative oxidase pathway decreased. In addition, checkpoints of mitochondrial energetic metabolism, mitochondrial ATP synthesis and transmembrane potential (ΔΨ), were tested, which showed that via interaction with AtVDAC3, AtKP1 down-regulated ATP synthesis while up-regulated AT. Taken together, AtKPl, along with its interaction with AtVDAC3, had crucial effect on regulating mitochondria1 functions.Furthermore, to explore the definite role of AtKP1 and AtVDAC3 interaction, a series of AtKP1 C-terminal truncated peptides were constructed, also their effects on mitochondrial functions were detected. To our surprise, different effects had been demonstrated among truncations as well as between truncations and full-length AtKP1. C-terminal 50 aa peptide C1038-1087, via interacted with AtVDAC3, up-regulated ATP synthesis while down-regulated ΔΨ; C988-1037 interacted with AtVDAC3 but had no effect on mitochondrial energetic metabolism; nevertheless, C-terminal 60 aa peptide C1028-1087 could not interact with AtVDAC3.Many researchers have reported that the release of mitochondrial cytochrome c acted as a significant checkpoint of apoptosis. Accordingly, our results indicated that AtKP1 regulated cytochrome c release and apoptosis via AtVDAC3.To sum up, results above demonstrated an interaction between the Arabidopsis kinesin AtKPl and mitochondrial outer membrane channel AtVDAC3. Both AtKP1 and AtVDAC3 were proved to be involved in ATP synthesis regulation, which maintained the balance of aerobic respiration, controlled cytochrome c release and apoptosis. These findings suggested a mechanism how plant motor proteins regulated energetic metabolism and mitochondria-mediated apoptosis, which provided new evidences for involvement of plant motor protein in mitochondrial function.