Details

Autor(en) / Beteiligte

• Son, Min-Jeong
• Kim, Joon-Chul
• Kim, Sung Woo
• Chidipi, Bojjibabu
• Muniyandi, Jeyaraj
• Singh, Thoudam Debraj
• So, Insuk
• Subedi, Krishna P
• Woo, Sun-Hee

Titel

Shear stress activates monovalent cation channel transient receptor potential melastatin subfamily 4 in rat atrial myocytes via type 2 inositol 1,4,5-trisphosphate receptors and Ca super(2+) release

Ist Teil von

• The Journal of physiology, 2016-06, Vol.594 (11), p.2985-3004

Erscheinungsjahr

2016

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• Key points * During each contraction and haemodynamic disturbance, cardiac myocytes are subjected to fluid shear stress as a result of blood flow and the relative movement of sheets of myocytes. * The present study aimed to characterize the shear stress-sensitive membrane current in atrial myocytes using the whole-cell patch clamp technique, combined with pressurized fluid flow, as well as pharmacological and genetic interventions of specific proteins. * The data obtained suggest that shear stress indirectly activates the monovalent cation current carried by transient receptor potential melastatin subfamily 4 channels via type 2 inositol 1,4,5-trisphosphate receptor-mediated Ca super(2+) release in subsarcolemmal domains of atrial myocytes. * Ca super(2+)-mediated interactions between these two proteins under shear stress may be an important mechanism by which atrial cells measure mechanical stress and translate it to alter their excitability. Atrial myocytes are subjected to shear stress during the cardiac cycle under physiological or pathological conditions. The ionic currents regulated by shear stress remain poorly understood. We report the characteristics, molecular identity and activation mechanism of the shear stress-sensitive current (I sub(shear)) in rat atrial myocytes. A shear stress of 16 dyn cm super(-2) was applied to single myocytes using a pressurized microflow system, and the current was measured by whole-cell patch clamp. In symmetrical CsCl solutions with minimal concentrations of internal EGTA, I sub(shear) showed an outwardly rectifying current-voltage relationship (reversal at -2 mV). The current was conducted primarily (80%) by monovalent cations but not Ca super(2+). It was suppressed by intracellular Ca super(2+) buffering at a fixed physiological level, inhibitors of transient receptor potential melastatin subfamily 4 (TRPM4), intracellular introduction of TRPM4 antibodies or knockdown of TRPM4 expression, suggesting that TRPM4 carries most of this current. A notable reduction in I sub(shear) occurred upon inhibition of Ca super(2+) release through the ryanodine receptors or inositol 1,4,5-trisphosphate receptors (IP sub(3)R) and upon depletion of sarcoplasmic reticulum Ca super(2+). In type 2 IP sub(3)R (IP sub(3)R2) knockout atrial myocytes, I sub(shear) was 10-20% of that in wild-type myocytes. Immunocytochemistry and proximity ligation assays revealed that TRPM4 and IP sub(3)R2 were expressed at peripheral sites with co-localization, although they are not localized within 40 nm. Peripheral localization of TRPM4 was intact in IP sub(3)R2 knockout cells. The data obtained in the present study suggest that shear stress activates TRPM4 current by triggering Ca super(2+) release from the IP sub(3)R2 in the peripheral domains of atrial myocytes. Key points * During each contraction and haemodynamic disturbance, cardiac myocytes are subjected to fluid shear stress as a result of blood flow and the relative movement of sheets of myocytes. * The present study aimed to characterize the shear stress-sensitive membrane current in atrial myocytes using the whole-cell patch clamp technique, combined with pressurized fluid flow, as well as pharmacological and genetic interventions of specific proteins. * The data obtained suggest that shear stress indirectly activates the monovalent cation current carried by transient receptor potential melastatin subfamily 4 channels via type 2 inositol 1,4,5-trisphosphate receptor-mediated Ca super(2+) release in subsarcolemmal domains of atrial myocytes. * Ca super(2+)-mediated interactions between these two proteins under shear stress may be an important mechanism by which atrial cells measure mechanical stress and translate it to alter their excitability.