The Patch-Clamp Technique for Measurement of K+Channels in Xenopus Oocytes and Mammalian Expression Systems

Abstract

Potassium channels are ubiquitous membrane proteins. They are expressed in most cells, both excitable and nonexcitable. In excitable cells, K+ channels preside over a wide range of cell functions such as excitability, propagation of excitation, and neurotransmitter release (Hille, 1992; Rudy, 1988). In nonexcitable cells, they are responsible for regulating cell volume and cell proliferation (Sobko et al., 1998; Hille, 1992). Therefore, most cells express different voltage-dependent K+ (Kv) channels to guarantee certain functions and to optimize the cellular response to different stimuli (Sobko et al., 1998; Conforti and Millhorn, 1997). The heteromultimeric nature of native Kv channels and the possibility that several related types of Kv channels of different compositions are expressed in the same cell complicate the study of an isolated channel in mammalian cells (Shamotienko et al., 1997; Sheng et al., 1993; Wang et al., 1993). Study of the behavior of a particular type of K+ channel in the native cell is further complicated by the limited selectivity of available K+ channel blockers and toxins (Hopkins, 1998; Grissmer et al., 1994). Kv channels of known composition can be expressed in heterologous expression systems, such as the Xenopus oocytes and mammalian cell lines. Structural and functional studies of Kv channels in expression systems provide important information for understanding, by extrapolation, the function of similar channels in native cells.