Reining SC Liesegang A Betz H Biber J Murer H Hernando N 2010 We have recently shown that the abundance of the renal sodium (Na)/inorganic phosphate (Pi) cotransporter NaPi-IIa is increased in the absence of the GABA(A) receptor-associated protein (GABARAP). Accordingly, GABARAP-deficient mice have a reduced urinary excretion of Pi. However, their circulating levels of Pi do not differ from wild-type animals, suggesting the presence of a compensatory mechanism responsible for keeping serum Pi values constant. Here, we aimed first to identify the molecular basis of this compensation by analyzing the expression of Na/Pi cotransporters known to be expressed in the kidney and intestine. We found that, in the kidney, the upregulation of NaPi-IIa is not accompanied by changes on the expression of either NaPi-IIc or PiT2, the other cotransporters known to participate in renal Pi reabsorption. In contrast, the intestinal expression of NaPi-IIb is downregulated in mutant animals, suggesting that a reduced intestinal absorption of Pi could contribute to maintain a normophosphatemic status despite the increased renal retention. The second goal of this work was to study whether the alterations on the expression of NaPi-IIa induced by chronic dietary Pi are impaired in the absence of GABARAP. Our data indicate that, in response to high Pi diets, GABARAP-deficient mice downregulate the expression of NaPi-IIa to levels comparable to those seen in wild-type animals. However, in response to low Pi diets, the upregulation of NaPi-IIa is greater in the mutant mice. Thus, both the basal expression and the dietary-induced upregulation of NaPi-IIa are increased in the absence of GABARAP. application/pdf https://sonar.ch/global/documents/211178 eng info:eu-repo/semantics/altIdentifier/doi/10.1007/s00424-010-0832-2 info:eu-repo/semantics/altIdentifier/pmid/20354864 info:eu-repo/semantics/openAccess Pflugers Archiv : European journal of physiology. - 2010 Animals Bone Density Cytoskeletal Proteins Femur Gene Expression Regulation Ileum Intestinal Absorption Kidney Lumbar Vertebrae Male Membrane Proteins Mice Mice, Inbred C57BL Mice, Knockout Microvilli Phosphates Phosphorus, Dietary RNA, Messenger Sodium Sodium-Phosphate Cotransporter Proteins, Type IIa Sodium-Phosphate Cotransporter Proteins, Type IIb Expression of renal and intestinal Na/Pi cotransporters in the absence of GABARAP. http://purl.org/coar/resource_type/c_6501