Role of T-type channels in vasomotor function: team player or chameleon?

• Published in: Pflügers Archiv 2014-04, Vol.466 (4), p.767-779
• Main Authors: Kuo, Ivana Y.-T., Howitt, Lauren, Sandow, Shaun L., McFarlane, Alexandra, Hansen, Pernille B., Hill, Caryl E.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Biomedical and Life Sciences; Biomedicine; Calcium Channels, T-Type - physiology; Cell Biology; Human Physiology; Humans; Invited Review; Membrane Potentials - physiology; Molecular Medicine; Molecular Sequence Data; Muscle, Smooth, Vascular - physiology; Neurosciences; Protein Isoforms - physiology; Receptors; Vasoconstriction - physiology; Vasodilation - physiology
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s00424-013-1430-x

Low-voltage-activated T-type calcium channels play an important role in regulating cellular excitability and are implicated in conditions, such as epilepsy and neuropathic pain. T-type channels, especially Cav3.1 and Cav3.2, are also expressed in the vasculature, although patch clamp studies of isolated vascular smooth muscle cells have in general failed to demonstrate these low-voltage-activated calcium currents. By contrast, the channels which are blocked by T-type channel antagonists are high-voltage activated but distinguishable from their L-type counterparts by their T-type biophysical properties and small negative shifts in activation and inactivation voltages. These changes in T-channel properties may result from vascular-specific expression of splice variants of Cav3 genes, particularly in exon 25/26 of the III–IV linker region. Recent physiological studies suggest that T-type channels make a small contribution to vascular tone at low intraluminal pressures, although the relevance of this contribution is unclear. By contrast, these channels play a larger role in vascular tone of small arterioles, which would be expected to function at lower intra-vascular pressures. Upregulation of T-type channel function following decrease in nitric oxide bioavailability and increase in oxidative stress, which occurs during cardiovascular disease, suggests that a more important role could be played by these channels in pathophysiological situations. The ability of T-type channels to be rapidly recruited to the plasma membrane, coupled with their subtype-specific localisation in signalling microdomains where they could modulate the function of calcium-dependent ion channels and pathways, provides a mechanism for rapid up- and downregulation of vasoconstriction. Future investigation into the molecules which govern these changes may illuminate novel targets for the treatment of conditions such as therapy-resistant hypertension and vasospasm.