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Protein phosphotyrosine phosphatase inhibitors suppress regulatory volume decrease and the volume-sensitive Cl-
S M Thoroed1, A Bryan-Sisneros, P Doroshenko
1Loeb Health Research Institute, 725 Parkdale Avenue, Ottawa, Ontario, K1Y 4E9, Canada.
Abstract:
The effects of the protein tyrosine phosphatase (PTP) inhibitors, pervanadate, monoperoxo(picolinato)- oxo-vanadate(V) [mpV(pic)] and dephostatin, on regulatory volume decrease (RVD) and the volume-sensitive Cl- current in mouse L-fibroblasts were studied with the aid of video microscopy and the whole-cell patch-clamp technique. The RVD induced by the hyposmotic shift from 300 to 150 mosmol/l, was strongly suppressed in cells that had been pre-incubated in pervanadate (25 microM) or in mpV(pic) (10 microM), or subjected to extracellular application of dephostatin (20 microM). The acceleration in RVD caused by gramicidin (0.5 microM) was also slowed down by pervanadate pre-treatment, suggesting that the PTP inhibitors affected the volume-sensitive Cl- conductance. Inhibition of the volume-sensitive Cl- current by pervanadate (25 microM) pre-treatment and by acutely applied dephostatin (20 microM) was confirmed in the whole-cell experiments (by @70% and by @50%, respectively). Both pervanadate and dephostatin inhibited the outward and inward Cl- currents equally, which suggests that only the number of open channels was affected. The amplitude of the Cl- current decreased slowly during application of dephostatin and did not recover after its termination. We conclude that in mouse L-fibroblasts, similar to bovine chromaffin cells, inhibition of PTPs results in the suppression of both RVD and the volume-sensitive Cl- current.
Insights
Protein tyrosine phosphatase (PTP) inhibitors, pervanadate and dephostatin, suppress regulatory volume decrease (RVD) and volume-sensitive chloride currents in mouse L-fibroblasts. This indicates PTP inhibition impacts cell volume regulation and ion transport.
Area of Science:
- Cellular Physiology
- Molecular Biology
- Biochemistry
Background:
- Regulatory volume decrease (RVD) is crucial for cell volume homeostasis.
- Volume-sensitive chloride currents play a key role in RVD.
- Protein tyrosine phosphatases (PTPs) are implicated in cellular signaling pathways.
Purpose of the Study:
- To investigate the effects of PTP inhibitors on RVD in mouse L-fibroblasts.
- To determine the impact of PTP inhibition on volume-sensitive chloride currents.
- To elucidate the role of PTPs in cell volume regulation.
Main Methods:
- Video microscopy for observing cell volume changes.
- Whole-cell patch-clamp technique for measuring chloride currents.
- Treatment with PTP inhibitors: pervanadate, monoperoxo(picolinato)-oxo-vanadate(V) [mpV(pic)], and dephostatin.
Main Results:
- Pervanadate, mpV(pic), and dephostatin significantly suppressed RVD induced by hyposmotic shock.
- PTP inhibitors reduced the acceleration of RVD caused by gramicidin.
- Pervanadate and dephostatin inhibited both outward and inward volume-sensitive chloride currents.
Conclusions:
- PTP inhibition suppresses RVD in mouse L-fibroblasts.
- PTP inhibitors affect the volume-sensitive chloride conductance.
- Inhibition of PTPs leads to the suppression of both RVD and volume-sensitive chloride currents, similar to findings in bovine chromaffin cells.