Abstract
Purpose :
How mitochondria communicate with the nucleus in apoptosis remain an intriguing question. The current study tested the hypothesis that mitochondrial trafficking could be determined by the retrograde signaling complex under stress conditions. To test our hypothesis, normal and aberrant mitochondrial networks were examined quantitatively based on mitochondrial size, shape, position, composition, and dynamics.
Methods :
The mitochondrial trafficking complex was isolated by immunoprecipitation using a prohibitin antibody. To understand mitochondrial structure and function, twelve categories, including (1) mitochondrial area, (2) cellular area, (3) mitochondrial content, (4) perimeter, (5) circularity, (6) average perimeter, (7) average mitochondrial area, (8) average circularity, (9) area/perimeter, (10) area/perimeter normalized to minor axis, (11) minor axis, (12) area/perimeter normalized to circularity, were calculated using ARPE-19 cells under oxidative stress. Mitochondrial localization and morphology were examined by immunocytochemistry.
Results :
The mitochondrial trafficking complex- kinesin, unknown protein at 110 kDa (myosin head motor domain, SH3 domain, ATP binding domain), unknown protein at 88 kDa (cadherin repeat, Ca2+ binding)- regulates mitochondrial size, morphology, and compositions. Kinesin-myosin-prohibitin interaction is involved in anterograde mitochondrial trafficking, whereas PKU beta S/T kinase-myosin-PI3K-lamin B2 bindings regulate an energy demanding retrograde transport of mitochondria. Prohibitin binding with a trafficking protein complex may regulate the bidirectional transport of mitochondria along actin microfilaments and microtubules. The mitocondrial trafficking complex may imply that a specific mechanism of communication may exist in the ATP and Ca+2 demanding regions. Total area of mitochondria decreased in 40-50% and both perimeter/circular mitochondria were downregulated up to 60-70%. Area/perimeter normalized to circularity ratio of mitochondria was decreased to 63% under oxidative stress.
Conclusions :
Mitochondrial dysfunction, altered dynamics, impaired transport, and turnover perturbation are associated with AMD. Impaired mitochondrial transport decreases the release of healthy mitochondria to distal processes, and disrupted eliminations of injured mitochondria may cause energy reduction and alteration of Ca2+ concentration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.