Journal Article

Scaffold protein harmonin (USH1C) provides molecular links between Usher syndrome type 1 and type 2

Jan Reiners, Erwin van Wijk, Tina Märker, Ulrike Zimmermann, Karin Jürgens, Heleen te Brinke, Nora Overlack, Ronald Roepman, Marlies Knipper, Hannie Kremer and Uwe Wolfrum

in Human Molecular Genetics

Volume 14, issue 24, pages 3933-3943
Published in print December 2005 | ISSN: 0964-6906
Published online November 2005 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddi417
Scaffold protein harmonin (USH1C) provides molecular links between Usher syndrome type 1 and type 2

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Usher syndrome (USH) is the most frequent cause of combined deaf-blindness in man. USH is clinically and genetically heterogeneous with at least 11 chromosomal loci assigned to the three USH types (USH1A-G, USH2A-C, USH3A). Although the different USH types exhibit almost the same phenotype in human, the identified USH genes encode for proteins which belong to very different protein classes and families. We and others recently reported that the scaffold protein harmonin (USH1C-gene product) integrates all identified USH1 molecules in a USH1-protein network. Here, we investigated the relationship between the USH2 molecules and this USH1-protein network. We show a molecular interaction between the scaffold protein harmonin (USH1C) and the USH2A protein, VLGR1 (USH2C) and the candidate for USH2B, NBC3. We pinpoint these interactions to interactions between the PDZ1 domain of harmonin and the PDZ-binding motifs at the C-termini of the USH2 proteins and NBC3. We demonstrate that USH2A, VLGR1 and NBC3 are co-expressed with the USH1-protein harmonin in the synaptic terminals of both retinal photoreceptors and inner ear hair cells. In hair cells, these USH proteins are also localized in the signal uptaking stereocilia. Our data indicate that the USH2 proteins and NBC3 are further partners in the supramolecular USH-protein network in the retina and inner ear which shed new light on the function of USH2 proteins and the entire USH-protein network. These findings provide first evidence for a molecular linkage between the pathophysiology in USH1 and USH2. The organization of USH molecules in a mutual ‘interactome’ related to the disease can explain the common phenotype in USH.

Journal Article.  7133 words.  Illustrated.

Subjects: Genetics and Genomics

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