Chapter 24 - A ragbag of channels

Abstract

ATP-gated ion channels, their structure and functional roles are discussed in this chapter. P2X receptors show different expression patterns and functional properties; their correlating structures and functions are also discussed. An example of vanilloid receptors like capsaicin (VR1) is seen because the vanilloid moiety is an essential component of capsaicin; this channel is called the “vanilloid receptor” (VR1). The ability of high temperatures to activate VR1 is covered in detail; this may explain the reason for capsaicin being perceived as hot. Whether an endogenous ligand for VR1 also exists is an interesting question. Some ion channels involved in programmed cell death are also described here. Beta-Amyloid peptide and its function in Alzheimer's disease is discussed, in most cases people with Down's syndrome may develop Alzheimer's disease. The mechanism of this toxicity is not com pletely clear and there are several contending views. One theory is that β-amyloid may contribute to neurodegeneration by inserting into the membrane to form an ion channel. This hypothesis is supported by the fact that β-amyloid forms ion channels in artificial lipid bilayers and induces a novel ion channel in hypothalamic neuronal membranes. Some members of the Bcl-2 family are intracellular membrane-associated proteins that regulate apoptosis, otherwise known as “programmed cell death.”