Simple oxygraphic analysis for the presence of adenylate kinase 1 and 2 in normal and tumor cells
Résumé
Background: Chronic obstructive pulmonary disease (COPD) is characterized by the inability of patients to sustain
a high level of ventilation resulting in perceived exertional discomfort and limited exercise capacity of leg muscles
at average intracellular ATP levels sufficient to support contractility.
Methods: Myosin ATPase activity in biopsy samples from healthy and COPD individuals was implemented as a
local nucleotide sensor to determine ATP diffusion coefficientswithin myofibrils. Ergometric parameters clinically
measured during maximal exercise tests in both groups were used to define the rates of myosin ATPase reaction
and aerobic ATP re-synthesis. The obtained parameters in combinationwith AK- and CK-catalyzed reactions
were implemented to compute the kinetic and steady-state spatial ATP distributions within control and COPD
sarcomeres.
Results: The developed reaction–diffusionmodel of two-dimensional sarcomeric space identified similar, yet extremely
low nucleotide diffusion in normal and COPD myofibrils. The corresponding spatio-temporal ATP distributions,
constructed during imposed exercise, predicted in COPD sarcomeres a depletion of ATP in the zones of
overlap between actin and myosin filaments along the center axis at average cytosolic ATP levels similar to
healthy muscles.
Conclusions: ATP-depleted zones can induce rigor tension foci impairing muscle contraction and increase a risk
for sarcomere damages. Thus, intra-sarcomeric diffusion restrictions at limited aerobic ATP re-synthesis can be
an additional risk factor contributing to the muscle contractile deficiency experienced by COPD patients.
General significance: This study demonstrates how restricted substrate mobility within a cellular organelle can
provoke an energy imbalance state paradoxically occurring at abounding average metabolic resources.