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Solute diffusion is hindered in the mitochondrial matrix.

ABSTRACT: Intracellular chemical reactions generally constitute reaction-diffusion systems located inside nanostructured compartments like the cytosol, nucleus, endoplasmic reticulum, Golgi, and mitochondrion. Understanding the properties of such systems requires quantitative information about solute diffusion. Here we present a novel approach that allows determination of the solvent-dependent solute diffusion constant (D(solvent)) inside cell compartments with an experimentally quantifiable nanostructure. In essence, our method consists of the matching of synthetic fluorescence recovery after photobleaching (FRAP) curves, generated by a mathematical model with a realistic nanostructure, and experimental FRAP data. As a proof of principle, we assessed D(solvent) of a monomeric fluorescent protein (AcGFP1) and its tandem fusion (AcGFP1(2)) in the mitochondrial matrix of HEK293 cells. Our results demonstrate that diffusion of both proteins is substantially slowed by barriers in the mitochondrial matrix (cristae), suggesting that cells can control the dynamics of biochemical reactions in this compartment by modifying its nanostructure.

SUBMITTER: Dieteren CE

PROVIDER: S-EPMC3102363 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Solute diffusion is hindered in the mitochondrial matrix.

Dieteren Cindy E J CE Gielen Stan C A M SC Nijtmans Leo G J LG Smeitink Jan A M JA Swarts Herman G HG Brock Roland R Willems Peter H G M PH Koopman Werner J H WJ

Proceedings of the National Academy of Sciences of the United States of America 20110509 21

Intracellular chemical reactions generally constitute reaction-diffusion systems located inside nanostructured compartments like the cytosol, nucleus, endoplasmic reticulum, Golgi, and mitochondrion. Understanding the properties of such systems requires quantitative information about solute diffusion. Here we present a novel approach that allows determination of the solvent-dependent solute diffusion constant (D(solvent)) inside cell compartments with an experimentally quantifiable nanostructure ...[more]

PMID: 21555543

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Project description:Osteocytes, the most abundant cells in bone, are essential in maintaining tissue homeostasis and orchestrating bone's mechanical adaptation. Osteocytes depend upon load-induced convection within the lacunar-canalicular system (LCS) to maintain viability and to sense their mechanical environment. Using the fluorescence recovery after photobleaching (FRAP) imaging approach, we previously quantified the convection of a small tracer (sodium fluorescein, 376 Da) in the murine tibial LCS under intermittent cyclic loading. In the present study, we first expanded the investigation of solute transport using a larger tracer (parvalbumin, 12.3 kDa), which is comparable in size to some signaling proteins secreted by osteocytes. Murine tibiae were subjected to sequential FRAP tests under rest-inserted cyclic loading while the loading magnitude (0, 2.8, or 4.8 N) and frequency (0.5, 1, or 2 Hz) were varied. The characteristic transport rate k and the transport enhancement relative to diffusion (k/k0) were measured under each loading condition, from which the peak solute velocity in the LCS was derived using our LCS transport model. Both the transport enhancement and solute velocity increased with loading magnitude and decreased with loading frequency. Furthermore, the solute-matrix interaction, quantified in terms of the reflection coefficient through the osteocytic pericellular matrix (PCM), was measured and theoretically modeled. The reflection coefficient of parvalbumin (? = 0.084) was derived from the differential fluid and solute velocities within loaded bone. Using a newly developed PCM sieving model, the PCM's fiber configurations accounting for the measured interactions were obtained for the first time. The present study provided not only new data on the micro-fluidic environment experienced by osteocytes in situ but also a powerful quantitative tool for future study of the PCM, the critical interface that controls both outside-in and inside-out signaling in osteocytes during normal bone adaptation and in pathological conditions.

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Solute diffusion is hindered in the mitochondrial matrix.

Publications

Solute diffusion is hindered in the mitochondrial matrix.

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