The actin cytoskeleton and small G protein RhoA are not involved in flow-dependent activation of ENaC.
BACKGROUND
Epithelial cells are exposed to a variety of mechanical stimuli. Epithelial Na+ channels (ENaC) mediate sodium transport across apical membranes of epithelial cells that line the distal nephron, airway and alveoli, and distal colon. Early investigations into stretch sensitivity of ENaC were controversial. However, recent studies are supportive of ENaC's mechanosensitivity. This work studied whether flow-dependent activation of ENaC is modulated by changes in the state of the actin cytoskeleton and whether small GTPase RhoA is involved in flow-mediated increase of ENaC activity.


RESULTS
Pretreatment with Cytochalasin D and Latrunculin B for 20 min and 1-2 hrs to disassemble F-actin had no effect on flow-mediated increase of amiloride-sensitive current. Overexpression of ENaC with constitutively active (G14V) or dominant negative (T19N) RhoA similarly had no effect on flow-dependent activation of ENaC activity. In addition, we did not observe changes when we inhibited Rho-kinase with Y27632.


CONCLUSIONS
Our results suggest that the flow-dependent activation of ENaC is not influenced by small GTPase RhoA and modifications in the actin cytoskeleton.
Karpushev
Alexey V
AV
Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd,, Milwaukee, WI 53226, USA. staruschenko@mcw.edu.
Ilatovskaya
Daria V
DV
Staruschenko
Alexander
A