54 This suggests that TRPC1 may not be an obligatory and/or exclusive component of the SFR (similar findings were reported for TRPC3 (http://www.ncbi.nlm.nih.gov/gene/7222) 55 ). However, as with all knockout experiments, there is always the possibility of compensatory changes in expression of other genes. One way of assessing order Ibrutinib this would be to use acute

knockdown experiments, ideally involving tissue-specific drivers of protein expression. It would also be instructive to explore acute MEF responses that would be expected to precede the SFR in cardiac myocytes or tissue preparations of TRPC1− / −  mice. TRPC6: Mammalian TRPC6 was initially identified as a mechanosensitive ion channel by Spassova et al., 56 who found that overexpression of TRPC6 in human embryonic kidney cell line 293 (HEK293) cells induced ISAC,NS. However, a subsequent study by Gottlieb et al. 50 found that TRPC6 overexpression in CHO and COS cells had no significant effect. More recently, it has

been suggested that TRPC6 is not mechanosensitive, unless co-expressed with the angiotensin II type 1 (AT1) receptor. 45,47 Data, more directly relevant for cardiac mechanosensitivity, came from Dyachenko et al., 58 who used mouse ventricular myocytes, as opposed to heterologous expression systems. Their whole-cell patch clamp experiments identified a robust ISAC,NS in response to shear stimuli, which was inhibited by pore-blocking TRPC6 antibodies. TRPC6 knockout blunts

the SFR in wild-type murine models, while its genetic down-regulation or pharmacological block returns ‘hyper-responsive’ murine models of Duchenne muscular dystrophy back to normal SFR levels, 55 highlighting the potential clinical relevance of targeted TRPC6 manipulation. TRPC6 is among a small number of SAC candidates that is highly expressed in human heart homogenates. 48 In murine heart, TRPC6 appears to be localised to T-tubules. 58 In agreement with this observation, detubulation GSK-3 inhibits ISAC,NS in murine cardiomyocytes. 58 Interestingly, a recent paper has suggested that the localization of TRPC6 shows marked plasticity in response to sympathetic stimulation via α1A receptors, and that these channels can translocate from T-tubules to the sarcolemma. 59 Whether this occurs physiologically is unclear; however, pre-treatment with α1A-agonists might serve as a useful experimental intervention to facilitate single-channel recordings of TRPC6, and potentially other channels localised in T-tubules, in adult ventricular myocytes. Other TRP channels: Several other members of the TRP family are mechanosensitive and are expressed in the heart. The TRPC3 protein has been identified in rat ventricular myocytes, also located in T-tubules.