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Claudin Expression and Function in the Kidney
APS Renal Section
Raymond C. Harris
A.S. Yu, R. Lifton, A. B. Singh and L. Gonzalez-Mariscal
A fundamental function of
the polarized epithelia is to maintain separation between apical and
basolateral compartments and to regulate the exchange of substances between
them. This regulation requires a barrier property, and tight junctions (TJs),
a belt of anatomizing strands of proteins and lipids around the lateral
membrane of epithelial cell create this barrier. Along the length of the
mammalian nephron, functional tight junction characteristics are remarkably
varied. Claudins have recently been identified as the integral structural
and functional transmembrane proteins of tight junctions, and their
functional importance has been demonstrated by identification of claudin
gene mutations that eliminate tight junctions in myelin and the testis,
abolish Mg2+ reabsorption in the kidney, and cause autosomal recessive
deafness. To date 24 members of this family have been identified that encode
proteins that range from ~20 to 27 kDa. However, each claudin exhibits a
distinct tissue-specific pattern of expression. Recent studies have begun to
identify the distribution pattern of the claudins in different nephron
segments and to examine their function in regulation of paracellular ionic
flux. The goal of the proposed symposium is to review the current state of
knowledge about claudin expression and function in the mammalian kidney.
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