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Author Notes:

Address for reprint requests and other correspondence: C. Chris Yun, Division of Digestive Diseases, Emory Univ. School of Medicine, Whitehead Bldg. Rm. 201, 615 Michael St., Atlanta, GA 30322 (e-mail: ccyun@emory.edu).

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Research Funding:

This work was supported by National Institutes of Health Grants (NIH) DK-061418 and DK-061418S1. P. He was supported by a postdoctoral fellowship from the American Heart Association.

Keywords:

  • proline-rich tyrosine kinase 2
  • extracellular signal-regulated kinase

Lysophosphatidic acid 5 receptor induces activation of Na+/H+ exchanger 3 via apical epidermal growth factor receptor in intestinal epithelial cells

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Journal Title:

American Journal of Physiology - Cell Physiology

Volume:

Volume 301, Number 5

Publisher:

, Pages C1008-C1016

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Na+ absorption is a vital process present in all living organisms. We have reported previously that lysophosphatidic acid (LPA) acutely stimulates Na+ and fluid absorption in human intestinal epithelial cells and mouse intestine by stimulation of Na+/H+ exchanger 3 (NHE3) via LPA5 receptor. In the current study, we investigated the mechanism of NHE3 activation by LPA5 in Caco-2bbe cells. LPA5-dependent activation of NHE3 was blocked by mitogen-activated protein kinase kinase (MEK) inhibitor PD98059 and U0126, but not by phosphatidylinositol 3-kinase inhibitor LY294002 or phospholipase C-β inhibitor U73122. We found that LPA5 transactivated the epidermal growth factor receptor (EGFR) and that inhibition of EGFR blocked LPA5-dependent activation of NHE3, suggesting an obligatory role of EGFR in the NHE3 regulation. Confocal immunofluorescence and surface biotinylation analyses showed that LPA5 was located mostly in the apical membrane. EGFR, on the other hand, showed higher expression in the basolateral membrane. However, inhibition of apical EGFR, but not basolateral EGFR, abrogated LPA-induced regulation of MEK and NHE3, indicating that LPA5 selectively activates apical EGFR. Furthermore, transactivation of EGFR independently activated the MEK-ERK pathway and proline-rich tyrosine kinase 2 (Pyk2). Similarly to MEK inhibition, knockdown of Pyk2 blocked activation of NHE3 by LPA. Furthermore, we showed that RhoA and Rho-associated kinase (ROCK) are involved in activation of Pyk2. Interestingly, LPA5 did not directly activate RhoA but was required for transactivation of EGFR. Together, these results unveil a pivotal role of apical EGFR in NHE3 regulation by LPA and show that the RhoA-ROCK-Pyk2 and MEK-ERK pathways converge onto NHE3.

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© 2011 the American Physiological Society

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