REGULATION OF CHLORIDE CHANNELS IN LYMPHOCYTES

The purpose of this chapter is to focus on chloride channels in T and B lymphocytes. It discusses their distribution, regulation, biophysical properties, and similarities with channels in other cell types, as determined primarily by patch-clamp experiments, and their possible role in lymphocyte functions. Before describing properties of the chloride channel subset, the chapter presents an overview of the other types of channels found (and not found) in lymphocytes. Patch-clamp techniques have been instrumental in identifying at least three types of Cl− channel in lymphocytes, categorized according to their single-channel conductance as mini-, midi-, and maxi-Cl− channels. These channels are normally closed in the plasma membrane of quiescent and proliferating cells, but are among the most abundant channels found in lymphocytes. Channel regulation is complex. The opening of each channel subtype depends upon at least two factors: ATP and cell swelling for the mini-Cl− channel, phosphorylation or excision/depolarization for the midi-Cl− channel, and excision and voltage for the maxi-Cl− channel. However, there remains confusion in the mechanism of opening of channels and other aspects of ion permeation properties. Considering all these, it can be concluded that the molecular identity of all three lymphocyte Cl- channels is still unknown. © 1994 Academic Press, Inc.