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Hensin, a new collecting duct protein involved in the in vitro plasticity of intercalated cell polarity.

ABSTRACT: Two forms of intercalated cells are present in kidney collecting tubules, the alpha cell has apical endocytosis, apical H+-ATPase and basolateral band 3, while beta cells have reversed polarity of these proteins and no apical endocytosis. When a beta cell line was seeded at high density, it changed into the alpha form. We previously showed that a partially purified 230 kD extracellular matrix protein of high density cells was able to retarget band 3 from apical to basolateral domains and stimulated apical endocytosis in vitro (Van Adelsberg, J., J.C. Edwards, J. Takito, B. Kiss, and Q. Al-Awqati. 1994. Cell. 76:1053-1061). We now purify this protein, which was named hensin, to near homogeneity and find that it belongs to the macrophage scavenger receptor cysteine rich (SRCR) family. An antibody, generated against a fusion protein made from a partial cDNA recognized a 230-kD protein in rabbit kidney and in the intercalated cell line. In vitro, the hensin antibody inhibited expression of apical endocytosis. Hensin was secreted in a polarized manner and bound to the basolateral membrane and extracellular matrix. Immunohistochemistry of the kidney showed that it was expressed only in collecting tubules. Double immunofluorescence with hensin and peanut lectin, H+-ATPase, or band 3 showed many patterns; most alpha-cells had hensin staining while 50% of beta-cells did not. These results suggest that hensin may also be involved in the polarity reversal of intercalated cells in vivo.

SUBMITTER: Takito J

PROVIDER: S-EPMC507683 | biostudies-other | 1996 Nov

REPOSITORIES: biostudies-other

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Hensin, a new collecting duct protein involved in the in vitro plasticity of intercalated cell polarity.

Takito J J Hikita C C Al-Awqati Q Q

The Journal of clinical investigation 19961101 10

Two forms of intercalated cells are present in kidney collecting tubules, the alpha cell has apical endocytosis, apical H+-ATPase and basolateral band 3, while beta cells have reversed polarity of these proteins and no apical endocytosis. When a beta cell line was seeded at high density, it changed into the alpha form. We previously showed that a partially purified 230 kD extracellular matrix protein of high density cells was able to retarget band 3 from apical to basolateral domains and stimula ...[more]

PMID: 8941650

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Project description:BACKGROUND:Retinoic acid is the bioactive derivative of vitamin A, which plays an indispensible role in kidney development by activating retinoic acid receptors. Although the location, concentration and roles of endogenous retinoic acid in post-natal kidneys are poorly defined, there is accumulating evidence linking post-natal vitamin A deficiency to impaired renal concentrating and acidifying capacity associated with increased susceptibility to urolithiasis, renal inflammation and scarring. The aim of this study is to examine the presence and the detailed localization of endogenous retinoic acid activity in neonatal, young and adult mouse kidneys, to establish a fundamental ground for further research into potential target genes, as well as physiological and pathophysiological roles of endogenous retinoic acid in the post-natal kidneys. METHODOLOGY/PRINCIPAL FINDINGS:RARE-hsp68-lacZ transgenic mice were employed as a reporter for endogenous retinoic acid activity that was determined by X-gal assay and immunostaining of the reporter gene product, ?-galactosidase. Double immunostaining was performed for ?-galactosidase and markers of kidney tubules to localize retinoic acid activity. Distinct pattern of retinoic acid activity was observed in kidneys, which is higher in neonatal and 1- to 3-week-old mice than that in 5- and 8-week-old mice. The activity was present specifically in the principal cells and the intercalated cells of the collecting duct system in all age groups, but was absent from the glomeruli, proximal tubules, thin limbs of Henle's loop and distal tubules. CONCLUSIONS/SIGNIFICANCE:Endogenous retinoic acid activity exists in principal cells and intercalated cells of the mouse collecting duct system after birth and persists into adulthood. This observation provides novel insights into potential roles for endogenous retinoic acid beyond nephrogenesis and warrants further studies to investigate target genes and functions of endogenous retinoic acid in the kidney after birth, particularly in the collecting duct system.

Dataset Information

Hensin, a new collecting duct protein involved in the in vitro plasticity of intercalated cell polarity.

Publications

Hensin, a new collecting duct protein involved in the in vitro plasticity of intercalated cell polarity.

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