Hence, it is expected that several of the protein disulphide bonds are disrupted upon UV illumination, inducing conformational changes that can affect the functionality of the biomolecule. It is well known that the microtubule-associated protein tau is expressed in the central and peripheral nervous system. However, tau is also found in many other tissues such as SP600125 citations kidney, lung, muscle, and breast. Tau is able to bind to both the outer and inner surfaces of microtubules, and plays an important role in promoting tubulin polymerization and stabilizing microtubules. Tau has been divided into four regions: an amino-terminal projection region, a proline-rich domain, a microtubule-binding domain, and an acidic carboxyl-terminal region. In adult human brain, six developmentally modulated isoforms are generated by alternative splicing around the amino-terminal region and MTB. The tau isoforms are distinct from each other by containing the different numbers of microtubule binding repeat sequences and amino-terminal exons. Numerous studies have indicated that abnormally hyperphosphorylated tau was involved in the formation of neurofibrillary tangles, a pathological hallmark of Alzheimer’s disease. Many serine and threonine residues on tau are phosphorylated by various kinases, which include glycogen synthase kinase 3, cyclic-AMP-dependent kinase, and microtubule-affinity regulating kinase. Dephosphorylation mediated by protein phosphatases counterbalances the effects of protein kinases; therefore, an imbalance of between protein kinases and protein phosphatases was considered as underlying mechanism of tau hyperphosphorylation in AD. The abnormal alterations of tau were also observed in many neurodegenerative disorders, and thus those diseases were referred to as tauopathies. Previous works have shown that estrogen was involved in improvement of neuronal survival and cognitive function. Ferreira et al reported that estrogen-enhanced neurite growth was mediated by promoting the levels of tau protein in dissociated cultures of hypothalamic neurons. In agreement with such study, overexpression of tau was able to promote neurite extension in cell culture. Moreover, tau was able to obstruct the binding of taxane and paclitaxel to the inner surface of microtubules, and thus reduced the sensitivity of breast cancer tissues with expression of estrogen receptors to these drugs, showing a promoting role of tau in tumor growth. These results implied that tau was capable to improve cell growth under some pathophysiological conditions. Ion channels have an essential role in cell proliferation and the development of cancer. On the other hand, cancer cells are, on average, more depolarized than healthy cells at the same histological origin. Kv channels, which contained six transmembrane segments and one pore-forming region, show a wide range of voltage dependence and kinetic properties. These channels are widely expressed in different kinds of excitable and non-excitable tissues, and have a crucial role in tuning action potential and neuronal excitability.