title: Renal expression of exchange protein directly activated by cAMP (Epac) 1 and 2.
abstract: In the kidney, many physiological processes of ion transport and cellular proliferation are mediated via cAMP, which classically activates protein kinase A (PKA). Recently, however, two new cAMP targets, the exchange protein directly activated by cAMP (Epac) 1 and 2, were identified, which mediate alternative pathways to PKA. To investigate their renal expression, antibodies specifically recognizing Epac1 and Epac2 were generated and used in rat immunohistochemistry with antibodies recognizing aquaporin-1 (AQP1), Tamm-Horsfall protein, Calbindin-D(28K), and AQP2 to mark proximal tubules (PT)/thin descending limbs of Henle's loop (tDLH), thick ascending limbs of Henle's loop (TAL), distal convoluted tubule/connecting tubule (DCT/CNT), and the collecting duct (CD) principal cells, respectively. Epac1 and Epac2 were expressed at the brush border of PT cells but were absent from tDLH cells. In the TAL, Epac1 and Epac2 were expressed throughout the cells with some confinement toward the apical membrane. In the DCT/CNT, Epac1 was confined to the apical region of the cells, whereas Epac2 was mainly expressed in the apical and basolateral regions. In the CD, a dispersed Epac1 expression was found in intercalated cells only (cortical CD), principal and intercalated cells [outer medullary CD (OMCD)], and mainly AQP2-negative cells in the inner medullary CD (IMCD). In contrast, Epac2 expression was at the apical and basolateral membrane of cortical principal cells, dispersed and apical in the OMCD, and in all cells of the IMCD. A similar distribution for Epac1/2 was found in the human kidney. The observed expression in different tubular segments suggests a major role for Epac 1/2 in tubular transport physiology and cellular proliferation.
authors.affiliation: Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Yuedan
authors.initials: Y
authors.lastname: Li
authors.forename: Irene B M
authors.initials: IB
authors.lastname: Konings
authors.forename: Jun
authors.initials: J
authors.lastname: Zhao
authors.forename: Leo S
authors.initials: LS
authors.lastname: Price
authors.forename: Emile
authors.initials: E
authors.lastname: de Heer
authors.forename: Peter M T
authors.initials: PM
authors.lastname: Deen
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000378:metabolism; D000918:Antibody Specificity; D002460:Cell Line; D049109:Cell Proliferation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008138:Loop of Henle / Q000166:cytology / Q000378:metabolism*; D008297:Male; D020033:Protein Isoforms / Q000276:immunology / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000906:Antibodies; D020662:Guanine Nucleotide Exchange Factors; D020033:Protein Isoforms; C116122:RAPGEF3 protein, human; C442864:RAPGEF4 protein, human; C526973:Rapgef3 protein, rat; C531571:Rapgef4 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases