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

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.


Related in: MedlinePlus

Protein turnover is diminished in microgravity.(A) A statistical box plot for the precursor amino acid ‘pool’ RIA calculated using the IH/IH and IH/IL forms of the double-lysine containing peptide EATNPPIIQEEKPK from Protein Disulfide Isomerase A3, including 48 h and 120 h time points. These data show no difference in the amino acid pool available for protein synthesis inside the cell between 1xg and μg condition (p = 0.80, Students T-test). (B) Statistical boxplots for RIA calculated for 359 highly-curated peptide pairs as a function of time under either 1xg or μg environment. Peptide RIA, a measure of protein turnover, was not different at 12 h (p = 0.32, Students T-test) but showed statistically significant slowing under μg at 48 and 120 h (p < 1e-6, Students T-test). Boxes represent quartiles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5037457&req=5

f3: Protein turnover is diminished in microgravity.(A) A statistical box plot for the precursor amino acid ‘pool’ RIA calculated using the IH/IH and IH/IL forms of the double-lysine containing peptide EATNPPIIQEEKPK from Protein Disulfide Isomerase A3, including 48 h and 120 h time points. These data show no difference in the amino acid pool available for protein synthesis inside the cell between 1xg and μg condition (p = 0.80, Students T-test). (B) Statistical boxplots for RIA calculated for 359 highly-curated peptide pairs as a function of time under either 1xg or μg environment. Peptide RIA, a measure of protein turnover, was not different at 12 h (p = 0.32, Students T-test) but showed statistically significant slowing under μg at 48 and 120 h (p < 1e-6, Students T-test). Boxes represent quartiles.

Mentions: Estimation of protein turnover requires the measurement of RIA of the precursor amino acid pool (essentially the maximum possible protein incorporation) by utilizing a peptide with more than one labeled residue1316. We assessed precursor amino acid RIA (r) using the peptide EATNPPIIQEEKPK in our data set (Supplemental Table 2-Peptide Expression) by the method of Doherty et al.16. Since this peptide contains two lysine (K) residues, the relative abundance of the heavy/heavy and heavy/light forms is dependent only on the ratio of the heavy and light lysine isotopes at the time of protein synthesis and is independent of protein turnover. This global measurement, defined as precursor RIA, was performed on data collected at 48 h and 120 h for both μg and 1xg (Fig. 3A). No significant difference in RIA was observed for the conditions (p = 0.80, Students T-test), indicating that the switch from light to heavy amino acid media was performed equally for both conditions. Additionally, since this is an intracellular measure of precursor amino acid, it indicates that there likely was no significant dysregulation in amino acid transporter function at the cell membrane between μg and 1xg. Collectively, these data suggest that incorporation of precursor amino acid (at least K and R) into proteins occurs similarly under both normal and microgravity conditions.


Microgravity induces proteomics changes involved in endoplasmic reticulum stress and mitochondrial protection
Protein turnover is diminished in microgravity.(A) A statistical box plot for the precursor amino acid ‘pool’ RIA calculated using the IH/IH and IH/IL forms of the double-lysine containing peptide EATNPPIIQEEKPK from Protein Disulfide Isomerase A3, including 48 h and 120 h time points. These data show no difference in the amino acid pool available for protein synthesis inside the cell between 1xg and μg condition (p = 0.80, Students T-test). (B) Statistical boxplots for RIA calculated for 359 highly-curated peptide pairs as a function of time under either 1xg or μg environment. Peptide RIA, a measure of protein turnover, was not different at 12 h (p = 0.32, Students T-test) but showed statistically significant slowing under μg at 48 and 120 h (p < 1e-6, Students T-test). Boxes represent quartiles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Protein turnover is diminished in microgravity.(A) A statistical box plot for the precursor amino acid ‘pool’ RIA calculated using the IH/IH and IH/IL forms of the double-lysine containing peptide EATNPPIIQEEKPK from Protein Disulfide Isomerase A3, including 48 h and 120 h time points. These data show no difference in the amino acid pool available for protein synthesis inside the cell between 1xg and μg condition (p = 0.80, Students T-test). (B) Statistical boxplots for RIA calculated for 359 highly-curated peptide pairs as a function of time under either 1xg or μg environment. Peptide RIA, a measure of protein turnover, was not different at 12 h (p = 0.32, Students T-test) but showed statistically significant slowing under μg at 48 and 120 h (p < 1e-6, Students T-test). Boxes represent quartiles.
Mentions: Estimation of protein turnover requires the measurement of RIA of the precursor amino acid pool (essentially the maximum possible protein incorporation) by utilizing a peptide with more than one labeled residue1316. We assessed precursor amino acid RIA (r) using the peptide EATNPPIIQEEKPK in our data set (Supplemental Table 2-Peptide Expression) by the method of Doherty et al.16. Since this peptide contains two lysine (K) residues, the relative abundance of the heavy/heavy and heavy/light forms is dependent only on the ratio of the heavy and light lysine isotopes at the time of protein synthesis and is independent of protein turnover. This global measurement, defined as precursor RIA, was performed on data collected at 48 h and 120 h for both μg and 1xg (Fig. 3A). No significant difference in RIA was observed for the conditions (p = 0.80, Students T-test), indicating that the switch from light to heavy amino acid media was performed equally for both conditions. Additionally, since this is an intracellular measure of precursor amino acid, it indicates that there likely was no significant dysregulation in amino acid transporter function at the cell membrane between μg and 1xg. Collectively, these data suggest that incorporation of precursor amino acid (at least K and R) into proteins occurs similarly under both normal and microgravity conditions.

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.


Related in: MedlinePlus