Increases in intracellular pH facilitate endocytosis and decrease availability of voltage-gated proton channels in...

Area of Science:

• Cellular Physiology
• Membrane Biology
• Ion Transport

Background:

• Voltage-gated proton channels (H(+) channels) facilitate proton transport across cell membranes.
• Channel activity is primarily governed by pH and voltage gradients, but current amplitudes can fluctuate unexpectedly.
• The regulation of H(+) channel availability at the plasma membrane remains incompletely understood.

Purpose of the Study:

• To investigate the role of intracellular pH (pHi) in regulating the number of available H(+) channels in osteoclasts and microglia.
• To determine the mechanism by which pHi affects H(+) channel conductance.

Main Methods:

• Whole-cell patch-clamp recordings were used to measure H(+) channel conductance.
• Intracellular pH was manipulated using NH4Cl exposure and washout.
• Endocytosis was assessed using FM1-43 uptake and quantified by changes in cell capacitance.
• The effect of dynasore, a dynamin blocker, on endocytosis and channel conductance was evaluated.

Main Results:

• Elevated pHi, induced by NH4Cl, led to a sustained decrease in H(+) channel conductance in osteoclasts and microglia.
• This decrease in conductance was associated with reduced cell capacitance and increased FM1-43 uptake, indicating enhanced endocytosis.
• The effect was not observed in COS7 cells expressing the murine H(+) channel (mVSOP).
• Dynasore treatment attenuated both the pHi-induced endocytosis and the reduction in H(+) channel conductance.

Conclusions:

• Increased intracellular pH facilitates dynamin-dependent endocytosis in osteoclasts and microglia.
• This pHi-induced endocytosis reduces the number of functional voltage-gated proton channels at the plasma membrane.
• Intracellular pH is a critical regulator of proton channel availability in these cell types.