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Plasma membrane calcium ATPase isoform expression in cultured rat mesangial cells
D Rouse1, J Abramowitz, X Zhou
1Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Abstract:
The maintenance of intracellular ionized calcium (iCa2+) in the submicromolar range is important for mesangial cell (MC) function, and, as in most mammalian cells, plasma membrane Ca(2+)-ATPases (PMCA) play an important role in the homeostatic process. Molecular studies have demonstrated four PMCA isoforms, each with multiple splice variants. The present study examines the expression of PMCA isoforms and calmodulin-binding region splice variants in cultured MC from Sprague-Dawley rats and from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats before and after the onset of hypertension in SHR. Using reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analyses, we have demonstrated PMCA1, -3, and -4, but not PMCA2, to be present in MC from these rat strains. Splice variant analysis revealed PMCA1a and -1b, PMCA3a, -3b, and -3c, and PMCA4a and -4b to be expressed in MC from all three strains. The relative quantities of PMCA1 and PMCA4 mRNA were not different in age-matched SHR vs. WKY rats, correlating with similar iCa2+ measurements. The expression of all three isoforms declined with age in SHR and WKY.
Insights
Plasma membrane Ca(2+)-ATPases (PMCA) are crucial for mesangial cell function. This study found PMCA1, -3, and -4 isoforms expressed in rat mesangial cells, with expression declining with age in both hypertensive and control rats.
Area of Science:
- Cell Biology
- Molecular Biology
- Physiology
Background:
- Intracellular ionized calcium (iCa2+) homeostasis is vital for mesangial cell (MC) function.
- Plasma membrane Ca(2+)-ATPases (PMCA) are key regulators of cellular calcium levels.
- Four PMCA isoforms with multiple splice variants are known in mammalian cells.
Purpose of the Study:
- To investigate the expression of PMCA isoforms and their splice variants in rat MC.
- To compare PMCA expression in cultured MC from normotensive (WKY) and spontaneously hypertensive (SHR) rats.
- To assess the impact of age and hypertension on PMCA expression in MC.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect PMCA mRNA.
- Southern blot analysis confirmed the presence of specific PMCA isoforms.
- Cultured mesangial cells from Sprague-Dawley, WKY, and SHR rats were utilized.
Main Results:
- PMCA1, -3, and -4 isoforms, but not PMCA2, were detected in rat MC.
- All analyzed splice variants of PMCA1, -3, and -4 were expressed across all rat strains.
- No significant differences in PMCA1 and PMCA4 mRNA levels were observed between SHR and WKY rats.
- PMCA expression in MC decreased with age in both SHR and WKY rats.
Conclusions:
- Rat MC express PMCA1, -3, and -4 isoforms, with specific splice variants present.
- Hypertension did not alter the relative expression of PMCA1 and PMCA4 mRNA in MC.
- Aging is associated with a decline in PMCA isoform expression in rat MC, irrespective of hypertensive status.