title: LPA stimulates intestinal DRA gene transcription via LPA2 receptor, PI3K/AKT, and c-Fos-dependent pathway.
abstract: DRA (downregulated in adenoma) or SLC26A3 is the major apical anion exchanger mediating Cl(-) absorption in intestinal epithelial cells. Disturbances in DRA function and expression have been implicated in diarrheal conditions such as congenital chloride diarrhea and inflammatory bowel diseases. Previous studies have shown that DRA is subject to regulation by short-term and transcriptional mechanisms. In this regard, we have recently shown that short-term treatment by lysophosphatidic acid (LPA), an important bioactive phospholipid, stimulates Cl(-)/HCO(3)(-)(OH(-)) exchange activity via an increase in DRA surface levels in human intestinal epithelial cells. However, the long-term effects of LPA on DRA at the level of gene transcription have not been examined. The present studies were aimed at investigating the effects of LPA on DRA function and expression as well as elucidating the mechanisms underlying its transcriptional regulation. Long-term LPA treatment increased the Cl(-)/HCO(3)(-) exchange activity in Caco-2 cells. LPA treatment (50-100 μM) of Caco-2 cells significantly stimulated DRA mRNA levels and DRA promoter activity (-1183/+114). This increase in DRA promoter activity involved the LPA2 receptor and phosphatidylinositol 3-kinase (PI3K)/AKT pathways. Progressive deletions from -1183/+114 to -790/+114 abrogated the stimulatory effects of LPA, indicating that the -1183/-790 promoter region harbors LPA response elements. Utilizing EMSA and mutational studies, our results showed that LPA induced the DRA promoter activity in a c-Fos-dependent manner. LPA also increased the protein expression of c-Fos and c-Jun in Caco-2 cells. Furthermore, overexpression of c-Fos but not c-Jun enhanced the DRA promoter activity. This increase in DRA transcription in response to LPA indicates that LPA may act as an antidiarrheal agent and could be exploited for the treatment of diarrhea associated with inflammatory or infectious diseases of the gut.
authors.affiliation: Section of Digestive Diseases and Nutrition, Dept. of Medicine, University of Illinois at Chicago, 60612, USA.
authors.forename: Amika
authors.initials: A
authors.lastname: Singla
authors.forename: Anoop
authors.initials: A
authors.lastname: Kumar
authors.forename: Shubha
authors.initials: S
authors.lastname: Priyamvada
authors.forename: Maliha
authors.initials: M
authors.lastname: Tahniyath
authors.forename: Seema
authors.initials: S
authors.lastname: Saksena
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Gill
authors.forename: Waddah A
authors.initials: WA
authors.lastname: Alrefai
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Dudeja
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism; D018938:Caco-2 Cells; D027963:Chloride-Bicarbonate Antiporters / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D016762:Genes, fos / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016758:Genes, jun / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000187:drug effects / Q000378:metabolism; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism*; D000076988:Sulfate Transporters; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D026905:Amino Acid Transport Systems; D027963:Chloride-Bicarbonate Antiporters; D008246:Lysophospholipids; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D049368:Receptors, Lysophosphatidic Acid; C081011:SLC26A3 protein, human; C475905:SLC36A1 protein, human; D000076988:Sulfate Transporters; D027981:Symporters; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; C032881:lysophosphatidic acid