Restricted Localization of Claudin-16 at the Tight Junction in the Thick Ascending Limb of Henle's Loop Together with Claudins 3, 4, and 10 in Bovine Nephrons

Abstract

ABSTRACT. Claudin-16 is one of the tight junction protein claudins and has been shown to contribute to reabsorption of divalent cations in the human kidney. In cattle, total deficiency of claudin-16 causes severe renal tubular dysplasia without aberrant metabolic changes of divalent cations, suggesting that bovine claudin-16 has some roles in renal tubule formation and paracellular transport that are somewhat different from those expected from the pathology of human disease. As the first step to clarify these roles, we examined the expression and distribution of claudin-16 and several other major claudin subtypes, claudins 1-4 and 10, in bovine renal tubular segments by immunofluorescence microscopy. Claudin-16 was exclusively distributed to the tight junction in the tubular segment positive for TammHorsfall glycoprotein, the thick ascending limb (TAL) of Henle's loop, and was found colocalized with claudins 3, 4, and 10. This study also demonstrates that bovine kidneys possess segment-specific expression patterns for claudins 2-4 and 10 that are different from those reported for mice. Particularly, distribution of claudin-4 in the TAL and distal convoluted tubules was characteristic of bovine nephrons as were differences in the expression patterns of claudins 2 and 3. These findings demonstrate that the total lack of claudin-16 in the TAL segment is the sole cause of renal tubular dysplasia in cattle and suggest that the tight junctions in distinct tubular segments including the TAL have barrier functions in paracellular permeability that are different among animal species. KEY WORDS: cattle, claudin-16, paracellular pathway, renal tubule, tight junction.J. Vet. Med. Sci. 68 (5): [453][454][455][456][457][458][459][460][461][462][463] 2006 Tight junctions (TJs) are located at the apicalmost region of lateral membranes of epithelial cells, and play a central role in sealing the intercellular space in epithelial cellular sheets. TJs create the primary barrier to the diffusion of solutes and water through the paracellular pathway and maintain cell polarity as a boundary between the apical and basolateral plasma membrane domains [7,26,29,34]. On freeze-fracture electron microscopy, TJs are visualized as a continuous anastomosing network of intramembranous particle strands, i.e., TJ strands, and complementary grooves [28]. The major components of TJ strands are the integral membrane proteins occludin and claudins, all of which have four transmembrane spans and two intervening extracellular loops [19]. Claudins consist of a family of more than 20 homologous subtypes, and they show tissue-specific and segment-specific distribution patterns in epithelia [19,29] such as those of the gastrointestinal tract [23] and renal tubules [15].Among these claudin proteins, claudin-16, formerly paracellin-1, has been shown to be responsible for inherited disease. Various mutations of the CLDN16 gene were reported to be the cause for familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) in the human [27]. Simon...

Deletion of claudin-10 ( Cldn10 ) in the thick ascending limb impairs paracellular sodium permeability and leads to hypermagnesemia and nephrocalcinosis

“…In the present study, mice lacking claudin-10 in the TAL presented with disturbances in the homeostasis of Ca 2+ and Mg 2+ homeostasis, as evidenced by hypocalcemia, hypermagnesemia, hyperphosphatemia, and nephrocalcinosis. Based on our data and that of others, the claudin-10 isoform expressed in this nephron segment is claudin-10b (9,17,18). Accordingly, using the ksp-cre mouse line, we specifically ablated claudin-10b expression in the TAL, but did not alter expression of claudin-10a in the PCT, as demonstrated by immunohistology and qPCR (Fig.…”

“…In cultured epithelial cells, heterologous expression of claudin-10a increases paracellular anion transport, whereas claudin-10b expression increases paracellular cation transport. Both isoforms are expressed differentially along the nephron, with claudin-10a found predominantly in cortical segments, whereas claudin-10b is enriched in the medullary region (9,17,18).…”

Lecture

“…CLDN5 and -15 are present only in endothelial cells; the rest are specifically expressed in different segments of the nephron. 41 Using antisera available at the time to perform immunostaining on mouse kidneys, 41 CLDN-3, -10, -11 and -16 were observed in the thick ascending limb (TAL), CLDN-3 and -8 in the distal convoluted tubule, and CLDN-3, -4 and -8 in the collecting duct (CLDN4 was also observed in the thick ascending limb 41 although absent in bovine TAL 42 ). CLDN2 is highly expressed in the "leaky" proximal nephron 43 consistent with its high cation selectivity when expressed in MDCK cells.…”

Claudin-10 exists in six alternatively spliced isoforms that exhibit distinct localization and function

“…As both the N-terminus and C-terminus reside in the cytoplasm, there are two extracellular loops through which claudins of neighbouring cells are assumed to interact, as they have been demonstrated to exhibit a barrier function and to regulate paracellular permeability (Wen et al, 2004;Hou et al, 2005). In tubular epithelia, a segment-specific distribution of different claudins is observed (Kiuchi-Saishin et al, 2002;Hashizume et al, 2004;Guan et al, 2005;Inai et al, 2005;Holmes et al, 2006;Ohta et al, 2006). Amongst these is claudin-10 which is differentially expressed along the length of many tubular epithelia including the nephron in the kidney.…”