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ANKS4B Is Essential for Intermicrovillar Adhesion Complex Formation.

ABSTRACT: Transporting and sensory epithelial cells shape apical specializations using protocadherin-based adhesion. In the enterocyte brush border, protocadherin function requires a complex of cytoplasmic binding partners, although the composition of this complex and logic governing its assembly remain poorly understood. We found that ankyrin repeat and sterile ? motif domain containing 4B (ANKS4B) localizes to the tips of adherent brush border microvilli and is essential for intermicrovillar adhesion. ANKS4B interacts with USH1C and MYO7B, which link protocadherins to the actin cytoskeleton. ANKS4B and USH1C also bind to the MYO7B cargo-binding tail at distinct sites. However, a tripartite complex only forms if ANKS4B and MYO7B are first activated by USH1C. This study uncovers an essential role for ANKS4B in brush border assembly, reveals a hierarchy in the molecular interactions that drive intermicrovillar adhesion, and informs our understanding of diseases caused by mutations in USH1C and ankyrin repeat proteins, such as Usher syndrome.

SUBMITTER: Crawley SW

PROVIDER: S-EPMC4730382 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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ANKS4B Is Essential for Intermicrovillar Adhesion Complex Formation.

Crawley Scott W SW Weck Meredith L ML Grega-Larson Nathan E NE Shifrin David A DA Tyska Matthew J MJ

Developmental cell 20160101 2

Transporting and sensory epithelial cells shape apical specializations using protocadherin-based adhesion. In the enterocyte brush border, protocadherin function requires a complex of cytoplasmic binding partners, although the composition of this complex and logic governing its assembly remain poorly understood. We found that ankyrin repeat and sterile α motif domain containing 4B (ANKS4B) localizes to the tips of adherent brush border microvilli and is essential for intermicrovillar adhesion. A ...[more]

PMID: 26812018

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Project description:Intestinal enterocytes have an elaborate apical membrane of actin-rich protrusions known as microvilli. The organization of microvilli is orchestrated by the intermicrovillar adhesion complex (IMAC), which connects the distal tips of adjacent microvilli. The IMAC is composed of CDHR2 and CDHR5 as well as the scaffolding proteins USH1C, ANKS4B, and Myosin 7b (MYO7B). To create an IMAC, cells must transport the proteins to the apical membrane. Myosin 5b (MYO5B) is a molecular motor that traffics ion transporters to the apical membrane of enterocytes, and we hypothesized that MYO5B may also be responsible for the localization of IMAC proteins. To address this question, we used two different mouse models: 1) neonatal germline MYO5B knockout (MYO5B KO) mice and 2) adult intestinal-specific tamoxifen-inducible VillinCreERT2;MYO5Bflox/flox mice. In control mice, immunostaining revealed that CDHR2, CDHR5, USH1C, and MYO7B were highly enriched at the tips of the microvilli. In contrast, neonatal germline and adult MYO5B-deficient mice showed loss of apical CDHR2, CDHR5, and MYO7B in the brush border and accumulation in a subapical compartment. Colocalization analysis revealed decreased Mander's coefficients in adult inducible MYO5B-deficient mice compared with control mice for CDHR2, CDHR5, USH1C, and MYO7B. Scanning electron microscopy images further demonstrated aberrant microvilli packing in adult inducible MYO5B-deficient mouse small intestine. These data indicate that MYO5B is responsible for the delivery of IMAC components to the apical membrane.NEW & NOTEWORTHY The intestinal epithelium absorbs nutrients and water through an elaborate apical membrane of highly organized microvilli. Microvilli organization is regulated by the intermicrovillar adhesion complexes, which create links between neighboring microvilli and control microvilli packing and density. In this study, we report a new trafficking partner of the IMAC, Myosin 5b. Loss of Myosin 5b results in a disorganized brush border and failure of IMAC proteins to reach the distal tips of microvilli.

Project description:Cleft palate results from a mixture of genetic and environmental factors and occurs when the bilateral palatal shelves fail to fuse. The objective of this study was to search for new genes involved in mouse palate formation. Gene expression of murine embryonic palatal tissue was analyzed at the various developmental stages before, during, and after palate fusion using GeneChip? microarrays. Ceacam1 was one of the highly up-regulated genes during and after fusion in palate formation, and this was confirmed by quantitative real-time PCR. Immunohistochemical staining showed that CEACAM1 was expressed at a very low level in palatal epithelium before fusion, but highly expressed in the midline of the palate during and after fusion. To investigate the developmental role of CEACAM1, function-blocking antibody was added to embryonic mouse palate in organ culture. Palatal fusion was inhibited by this function-blocking antibody. To investigate the subsequent developmental role of CEACAM1, we characterized Ceacam1-deficient (Ceacam1-/-) mice. Epithelial cells persisted abnormally at the midline of the embryonic palate even on day E16.0, and palatal fusion was delayed in Ceacam1-/- mice. TGF?3 expression, apoptosis, and cell proliferation in palatal epithelium were not effected in the palate of Ceacam1-/-mice. CEACAM1 expression was down-regulated in Tgfb3-/- palate. However, exogenous TGF?3 did not induce CEACAM1 expression. These results suggest that CEACAM1 has roles in both the initiation of palate formation via epithelial cell adhesion and TGF signaling has some indirect effect on CEACAM1. Global gene expression profiling of palatal processes before, during and after fusion of palatal shelves We used microarray to investigate the gene expression of palatal tissue during palatal development. Palatal processes were microdissected at the stages of palatal development (before, during and after fusion) for RNA extraction and hybridization on Affymetrix microarrays.

Dataset Information

ANKS4B Is Essential for Intermicrovillar Adhesion Complex Formation.

Publications

ANKS4B Is Essential for Intermicrovillar Adhesion Complex Formation.

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