Lysophosphatidic acid stimulates the intestinal brush border Na(+)/H(+) exchanger 3 and fluid absorption via LPA(5) and NHERF2.
OBJECTIVE
Diarrhea results from reduced net fluid and salt absorption caused by an imbalance in intestinal absorption and secretion. The bulk of sodium and water absorption in the intestine is mediated by Na(+)/H(+) exchanger 3 (NHE3), located in the luminal membrane of enterocytes. We investigated the effect of lysophosphatidic acid (LPA) on Na(+)/H(+) exchanger activity and Na(+)-dependent fluid absorption in the intestine.


METHODS
We analyzed the effects of LPA on fluid absorption in intestines of wild-type mice and mice deficient in Na(+)/H(+) exchanger regulatory factor 2 (NHERF2; Nherf2(-/-)) or LPA(2) (Lpa(2)(-/-)). Roles of LPA(5) and NHERF2 were determined by analysis of heterologous expression.


RESULTS
Under basal conditions, LPA increased fluid absorption in an NHE3-dependent manner and restored the net fluid loss in a mouse model of acute diarrhea. Expression of the LPA receptor LPA(5) was necessary for LPA-induced stimulation of NHE3 activity in colonic epithelial cells. Stimulation of NHE3 by the LPA-LPA(5) signaling required coexpression of NHERF2, which interacted with LPA(5). LPA-mediated intestinal fluid absorption was impaired in Nherf2(-/-) mice, demonstrating the requirement for NHERF2 in LPA(5) activity. However, fluid absorption was unaltered in Lpa(2)(-/-) mice. LPA stimulated NHE3 and fluid absorption in part by increasing NHE3 protein abundance at the brush border membrane of intestinal epithelial cells.


CONCLUSIONS
LPA is a potent stimulant of NHE3 and fluid absorption in the intestine, signaling through LPA(5). Regulation by LPA(5) depends on its interaction with NHERF2. LPA might be useful in the treatment of certain diarrheal diseases.
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Songbai
S
Lin
Sunil
S
Yeruva
Peijian
P
He
Anurag Kumar
AK
Singh
Huanchun
H
Zhang
Mingmin
M
Chen
Georg
G
Lamprecht
Hugo R
HR
de Jonge
Ming
M
Tse
Mark
M
Donowitz
Boris M
BM
Hogema
Jerold
J
Chun
Ursula
U
Seidler
C Chris
CC
Yun
D000818:Animals; D003106:Colon / Q000378:metabolism*; D003967:Diarrhea / Q000378:metabolism; D004195:Disease Models, Animal; D007408:Intestinal Absorption / Q000502:physiology*; D008246:Lysophospholipids / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014867:Water / Q000378:metabolism
C548235:LPAR5 protein, mouse; D008246:Lysophospholipids; D010750:Phosphoproteins; D049368:Receptors, Lysophosphatidic Acid; C000613386:Slc9a3 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D014867:Water; C032881:lysophosphatidic acid