Formation of aberrant TJ strands by overexpression of claudin-15 in MDCK II cells |
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Authors: | Akihito Sengoku Tetsuichiro Inai Yosaburo Shibata |
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Institution: | (1) Department of Developmental Molecular Anatomy, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-Ku, 812-8582 Fukuoka, Japan |
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Abstract: | Claudins are one of the transmembrane proteins found at tight junctions (TJs); they constitute the backbone of TJ strands
and comprise a multigene family. Claudins share a YV sequence at the COOH-termini, which is considered to be a ZO-binding
motif. Overexpression of claudin-15 (15CL) or claudin-15 tagged with enhanced green fluorescent protein at the NH2-terminus (EGFP-15CL) induced aberrant strands in MDCK II cells, even though claudin-15 has the ZO-binding motif. Morphometric
analysis by freeze-fracture electron microscopy revealed that the mean number of apical TJ strands increased by 47% in EGFP-1CL-expressing
cells, 21% in EGFP-15CL-expressing cells, and 28% in 15CL-expressing cells. The number of free-ended apical strands increased
remarkably in EGFP-15CL- and 15CL-expressing cells, but not in EGFP-1CL-expressing cells. When MDCK cells expressing EGFP-1CL,
EGFP-15CL or 15CL were co-cultured with parent MDCK cells, which express claudin-1 but not claudin-15, EGFP-15CL and 15CL
could not be concentrated at the apical junctional region between the heterotypic cells, though EGFP-1CL could. These results
suggest that not only binding to ZO-1, but also head-to-head compatibility between claudin species, is involved in organizing
claudin proteins at the apical junctional region. |
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Keywords: | Tight junction Claudin ZO-1 MDCK cell Freeze fracture |
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