TRPC channels and their implications for neurological diseases

Calcium is an essential intracellular messenger and serves critical cellular functions in both excitable and non-excitable cells. Most of the physiological functions in these cells are uniquely regulated by changes in cytosolic Ca²⁺ levels ([Ca²⁺]_i), which are achieved via various mechanisms. One of these mechanism(s) is activated by the release of Ca²⁺ from the endoplasmic reticulum (ER), followed by Ca²⁺ influx across the plasma membrane (PM). Activation of PM Ca ²⁺ channels is essential for not only refilling of the ER Ca ²⁺ stores, but is also critical for maintaining [Ca ²⁺]_i that regulates biological functions, such as neurosecretion, sensation, long term potentiation, synaptic plasticity, gene regulation, as well as cellular growth and differentiation. Alterations in Ca²⁺ homeostasis have been suggested in the onset/progression of neurological diseases, such as Parkinson's, Alzheimer's, bipolar disorder, and Huntington's diseases. Available data on transient receptor potential conical (TRPC) protein indicate that these proteins initiate Ca²⁺ entry pathways and are essential in maintaining cytosolic, ER, and mitochondrial Ca²⁺ levels. A number of biological functions have been assigned to these TRPC proteins. Silencing of TRPC1 and TRPC3 has been shown to inhibit neuronal proliferation and loss of TRPC1 is implicated in neurodegeneration. Thus, TRPC channels not only contribute towards normal physiological processes, but are also implicated in several human pathological conditions. Overall, it is suggested that these channels could be used as potential therapeutic targets for many of these neurological diseases. Thus, in this review we have focused on the functional implication of TRPC channels in neuronal cells along with the elucidation of their role in neurodegeneration.