Src Family Kinase Links Insulin Signaling to Short Term Regulation of Na, K‐ATPase in Nonpigmented Ciliary Epithelium. Issue 6 (10th November 2016)

• Record Type: Journal Article
• Authors: Shahidullah, Mohammad; Mandal, Amritlal; Delamere, Nicholas A.
• Is Part Of: Journal of cellular physiology. Volume 232:Issue 6(2017:Jun.)
• Page Start: 1489
• Page End: 1500
• Publication Date: 2016-11-10
• Subjects: Physiology -- Periodicals; Cell physiology -- Periodicals; 571.6
• DOI: 10.1002/jcp.25654
• Languages: English
• ISSNs: 0021-9541

Abstract

Abstract : Insulin has been shown to elicit changes of Na, K‐ATPase activity in various tissues. Na, K‐ATPase in the nonpigmented ciliary epithelium (NPE) plays a role in aqueous humor secretion and changes of Na, K‐ATPase activity impact the driving force. Because we detect a change of NPE Na, K‐ATPase activity in response to insulin, studies were carried out to examine the response mechanism. Ouabain‐sensitive rubidium (Rb) uptake by cultured NPE cells, measured as a functional index of Na, K‐ATPase‐mediated inward potassium transport, was found to increase in cells exposed for 5 min to insulin. The maximally effective concentration was 100 nM. An intrinsic increase of Na, K‐ATPase activity evident as a >2‐fold increase in the rate of ouabain‐sensitive ATP hydrolysis in homogenates obtained from cells exposed to 100 nM insulin for 5 min was also observed. Insulin‐treated cells exhibited Akt, Src family kinase (SFK), ERK1/2, and p38 activation, all of which were prevented by a pI3 kinase inhibitor LY294002. The Rb uptake and Na, K‐ATPase activity response to insulin both were abolished by PP2, an SFK inhibitor which also prevented p38 and ERK1/2 but not Akt activation. The Akt inhibitor MK‐2206 did not change the Na, K‐ATPase response to insulin. The findings suggest insulin activates pI3K‐dependent Akt and SFK signaling pathways that are separate. ERK1/2 and p38 activation is secondary to and dependent on SFK activation. The increase of Na, K‐ATPase activity is dependent on activation of the SFK pathway. The findings are consistent with previous studies that indicate a link between Na, K‐ATPase activity and SFK signaling. J. Cell. Physiol. 232: 1489–1500, 2017. © 2016 Wiley Periodicals, Inc. Abstract : Studies were conducted to examine the insulin response in ocular nonpigmented ciliary epithelium. Insulin elicited a pronounced short term increase in Na, K‐ATPase activity and a complex signaling response that involved Akt (protein kinase B), Src family kinase (SFK), ERK1/2, and p38 MAPK all of which were dependent on PI3K activation. ERK1/2 and p38 MAPK activation were secondary to and dependent on SFK activation. The insulin‐dependent increase in Na, K‐ATPase activity was linked to SFK activation. In contrast, Akt activation has no discernable effect on Na, K‐ATPase activity.