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Microgravity induces proteomics changes involved in endoplasmic reticulum stress and mitochondrial protection

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ABSTRACT

On Earth, biological systems have evolved in response to environmental stressors, interactions dictated by physical forces that include gravity. The absence of gravity is an extreme stressor and the impact of its absence on biological systems is ill-defined. Astronauts who have spent extended time under conditions of minimal gravity (microgravity) experience an array of biological alterations, including perturbations in cardiovascular function. We hypothesized that physiological perturbations in cardiac function in microgravity may be a consequence of alterations in molecular and organellar dynamics within the cellular milieu of cardiomyocytes. We used a combination of mass spectrometry-based approaches to compare the relative abundance and turnover rates of 848 and 196 proteins, respectively, in rat neonatal cardiomyocytes exposed to simulated microgravity or normal gravity. Gene functional enrichment analysis of these data suggested that the protein content and function of the mitochondria, ribosomes, and endoplasmic reticulum were differentially modulated in microgravity. We confirmed experimentally that in microgravity protein synthesis was decreased while apoptosis, cell viability, and protein degradation were largely unaffected. These data support our conclusion that in microgravity cardiomyocytes attempt to maintain mitochondrial homeostasis at the expense of protein synthesis. The overall response to this stress may culminate in cardiac muscle atrophy.

No MeSH data available.


Surrogates of cell damage and protein degradation.(A) LDH release was not significantly different among groups (n = 4). (B) Caspase-3 activity was not different among groups (n = 3). (C) A bar chart representing the immunoblot of protein ubiquitination; there was no significant difference among groups. (D) Representative immunoblot of ubiquitinated proteins using antibody clone P4D1 (n = 3). LDH, lactate dehydrogenase; RLU, relative light unit.
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f5: Surrogates of cell damage and protein degradation.(A) LDH release was not significantly different among groups (n = 4). (B) Caspase-3 activity was not different among groups (n = 3). (C) A bar chart representing the immunoblot of protein ubiquitination; there was no significant difference among groups. (D) Representative immunoblot of ubiquitinated proteins using antibody clone P4D1 (n = 3). LDH, lactate dehydrogenase; RLU, relative light unit.

Mentions: Proteomics and gene set enrichment analyses indicate that microgravity differentially influences processes in the cytoplasm and mitochondria. Nonetheless, it is possible that microgravity exposure augments cell injury, contributing to the observed differences. To investigate this possibility the media from cells placed in 1xg and μg conditions was examined for lactate dehydrogenase (LDH) levels at ten time points between 0 and 120 h (Fig. 5A). LDH is a soluble cytosolic enzyme, and its release is an indication of cell membrane permeability or damage. No statistically significant difference in LDH release from the cell was observed between μg and 1xg at any time point, although LDH was elevated at 24 and 96 h compared to at 1 h within the μg group (p < 0.05, Repeated-measures ANOVA, n = 4; Fig. 5A). These data suggest that proteomic differences are not due to enhanced physical cell injury during microgravity exposure.


Microgravity induces proteomics changes involved in endoplasmic reticulum stress and mitochondrial protection
Surrogates of cell damage and protein degradation.(A) LDH release was not significantly different among groups (n = 4). (B) Caspase-3 activity was not different among groups (n = 3). (C) A bar chart representing the immunoblot of protein ubiquitination; there was no significant difference among groups. (D) Representative immunoblot of ubiquitinated proteins using antibody clone P4D1 (n = 3). LDH, lactate dehydrogenase; RLU, relative light unit.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037457&req=5

f5: Surrogates of cell damage and protein degradation.(A) LDH release was not significantly different among groups (n = 4). (B) Caspase-3 activity was not different among groups (n = 3). (C) A bar chart representing the immunoblot of protein ubiquitination; there was no significant difference among groups. (D) Representative immunoblot of ubiquitinated proteins using antibody clone P4D1 (n = 3). LDH, lactate dehydrogenase; RLU, relative light unit.
Mentions: Proteomics and gene set enrichment analyses indicate that microgravity differentially influences processes in the cytoplasm and mitochondria. Nonetheless, it is possible that microgravity exposure augments cell injury, contributing to the observed differences. To investigate this possibility the media from cells placed in 1xg and μg conditions was examined for lactate dehydrogenase (LDH) levels at ten time points between 0 and 120 h (Fig. 5A). LDH is a soluble cytosolic enzyme, and its release is an indication of cell membrane permeability or damage. No statistically significant difference in LDH release from the cell was observed between μg and 1xg at any time point, although LDH was elevated at 24 and 96 h compared to at 1 h within the μg group (p < 0.05, Repeated-measures ANOVA, n = 4; Fig. 5A). These data suggest that proteomic differences are not due to enhanced physical cell injury during microgravity exposure.

View Article: PubMed Central - PubMed

ABSTRACT

On Earth, biological systems have evolved in response to environmental stressors, interactions dictated by physical forces that include gravity. The absence of gravity is an extreme stressor and the impact of its absence on biological systems is ill-defined. Astronauts who have spent extended time under conditions of minimal gravity (microgravity) experience an array of biological alterations, including perturbations in cardiovascular function. We hypothesized that physiological perturbations in cardiac function in microgravity may be a consequence of alterations in molecular and organellar dynamics within the cellular milieu of cardiomyocytes. We used a combination of mass spectrometry-based approaches to compare the relative abundance and turnover rates of 848 and 196 proteins, respectively, in rat neonatal cardiomyocytes exposed to simulated microgravity or normal gravity. Gene functional enrichment analysis of these data suggested that the protein content and function of the mitochondria, ribosomes, and endoplasmic reticulum were differentially modulated in microgravity. We confirmed experimentally that in microgravity protein synthesis was decreased while apoptosis, cell viability, and protein degradation were largely unaffected. These data support our conclusion that in microgravity cardiomyocytes attempt to maintain mitochondrial homeostasis at the expense of protein synthesis. The overall response to this stress may culminate in cardiac muscle atrophy.

No MeSH data available.