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Anion exchanger isoform 2 operates in parallel with Na(+)/H(+) exchanger isoform 1 during regulatory volume decrease
Meng Ru Shen1, Robert J Wilkins, Cheng Yang Chou
1University Laboratory of Physiology, Oxford, UK.
FEBS Letters
|February 20, 2002
Summary
Intracellular pH regulation in cervical cancer cells during volume changes involves Na+/H+ exchanger 1 (NHE1) and anion exchanger 2 (AE2). These transporters work together to maintain pH balance in SiHa cells experiencing regulatory volume decrease (RVD).
Area of Science:
- Cell Biology
- Physiology
- Biochemistry
Background:
- Intracellular pH (pH(i)) homeostasis is crucial for cell function.
- Regulatory Volume Decrease (RVD) is a cellular response to osmotic stress.
- Understanding ion transport during RVD in cancer cells is important for disease research.
Purpose of the Study:
- To investigate the role of specific ion transport systems in regulating intracellular pH during RVD in human cervical cancer SiHa cells.
- To identify the key transporters involved in maintaining pH(i) homeostasis under hypotonic conditions.
Main Methods:
- Reverse transcriptase polymerase chain reaction (RT-PCR) to detect mRNA transcripts of Na+/H+ exchanger (NHE) and anion exchanger (AE) isoforms.
- Western immunoblotting to confirm protein expression of NHE1 and AE2.
- Fluorescent dye measurements of intracellular pH changes in SiHa cells subjected to hypotonic stress.
- Pharmacological inhibition of NHE and AE transporters.
Main Results:
- SiHa cells express mRNA for NHE1, NHE3, and AE2.
- Hypotonic stress induced intracellular acidification, which was enhanced by NHE inhibitors and absence of extracellular Na+, indicating NHE1's role in compensation.
- Extracellular chloride was essential for pH(i) acidification during RVD.
- AE2 inhibition significantly attenuated hypotonicity-induced acidification, suggesting its role in mediating Cl- influx and HCO3- efflux.
Conclusions:
- The Na+/H+ exchanger isoform 1 (NHE1) plays a primary role in compensating for intracellular acidification during RVD in SiHa cells.
- The anion exchanger isoform 2 (AE2) functions in parallel with NHE1, mediating Cl- influx to regulate pH(i) homeostasis.
- Both NHE1 and AE2 are critical for maintaining pH(i) during regulatory volume decrease in human cervical cancer cells.