Vendelin 2017 Abstract MITOEAGLE Barcelona

Most of mitochondrial voltage-dependent anion channels are closed in rat cardiomyocytes

Link: MitoEAGLE

Vendelin M (2017)

Event: MitoEAGLE Barcelona 2017

Regulation of mitochondrial respiration in response to the change in the mechanical workload is a vital process in the heart. As a part of the regulatory system, the physical intracellular environment surrounding mitochondria governs molecular movement and, in particular, the movement of signaling molecules from the surroundings to the mitochondria. Earlier, we have demonstrated that there are two types of diffusion obstacles that interfere with the signaling between ATPases and mitochondria: the mitochondrial outer membrane (mtOM), which is permeable to small hydrophilic molecules through the voltage-dependent anion channel (VDAC), and cytoplasmatic diffusion barriers grouping ATP-producers and -consumers. However, the contribution of each of these diffusion obstacles to the overall restriction of molecular diffusion in cardiomyocytes is not known. While it has been demonstrated by several groups that VDAC opening can be regulated by its interaction with cytoskeletal proteins, the number of open VDACs in vivo remains unknown.

The aim of this work was to establish the partitioning of intracellular diffusion obstacles in cardiomyocytes. For that, we took advantage of the relationship between NADH autofluorescence and mitochondrial respiration that we found earlier on permeabilized cardiomyocytes. We studied the response of mitochondrial oxidative phosphorylation of permeabilized rat cardiomyocytes to changes in extracellular ADP by recording 3D image stacks of NADH autofluorescence. Using cell-specific mathematical models, we determined the permeability of mtOM and cytoplasmatic barriers. We found that only ~ 2% of VDACs are accessible to cytosolic ADP and cytoplasmatic diffusion barriers reduce the apparent diffusion coefficient by 6–10 ×. Such a small number of open VDACs indicates that most of mitochondrial VDACs are shielded by intracellular structures and interact with the surroundings through microcompartments and/or are closed through interaction with, for example, tubulin.

Our findings show that in cardiomyocytes, diffusion barriers in the cytoplasm and by the mtOM restrict ADP/ATP diffusion to similar extents suggesting a major role of both barriers in energy transfer and other intracellular processes.

• Bioblast editor: Kandolf G

Labels: MiParea: Respiration, mt-Membrane 

Organism: Rat  Tissue;cell: Heart  Preparation: Permeabilized cells 

Regulation: ADP 

HRR: Oxygraph-2k  Event: A2 

Affiliations

Lab Systems Biol, Dept Cybernetics, School Sc, Tallinn Univ Technology, Estonia