Otoferlin interacts with myosin VI: implications for maintenance of the basolateral synaptic structure of the inner hair cell

• Published in: Human molecular genetics Vol. 18; no. 15; pp. 2779 - 2790
• Main Authors: Heidrych, Paulina, Zimmermann, Ulrike, Kuhn, Stephanie, Franz, Christoph, Engel, Jutta, Duncker, Susanne V., Hirt, Bernhard, Pusch, Carsten M., Ruth, Peter, Pfister, Markus, Marcotti, Walter, Blin, Nikolaus, Knipper, Marlies
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.08.2009; Oxford Publishing Limited (England)
• Subjects: Amino Acid Sequence; Animals; Biological and medical sciences; Calcium - metabolism; Deafness - genetics; Deafness - metabolism; Disease Models, Animal; Exocytosis; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Hair Cells, Auditory, Inner - chemistry; Hair Cells, Auditory, Inner - metabolism; Humans; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Mice, Transgenic; Molecular and cellular biology; Molecular Sequence Data; Myosin Heavy Chains - chemistry; Myosin Heavy Chains - genetics; Myosin Heavy Chains - metabolism; Protein Binding; Protein Transport; Synapses - chemistry; Synapses - metabolism; Two-Hybrid System Techniques; Hair; Genetics; Molecular motor; Myosin
• DOI: 10.1093/hmg/ddp213
• ISSN: 0964-6906

Otoferlin has been proposed to be the Ca2+ sensor in hair cell exocytosis, compensating for the classical synaptic fusion proteins synaptotagmin-1 and synaptotagmin-2. In the present study, yeast two-hybrid assays reveal myosin VI as a novel otoferlin binding partner. Co-immunoprecipitation assay and co-expression suggest an interaction of both proteins within the basolateral part of inner hair cells (IHCs). Comparison of otoferlin mutants and myosin VI mutant mice indicates non-complementary and complementary roles of myosin VI and otoferlin for synaptic maturation: (i) IHCs from otoferlin mutant mice exhibited a decoupling of CtBP2/RIBEYE and CaV1.3 and severe reduction of exocytosis. (ii) Myosin VI mutant IHCs failed to transport BK channels to the membrane of the apical cell regions, and the exocytotic Ca2+ efficiency did not mature. (iii) Otoferlin and myosin VI mutant IHCs showed a reduced basolateral synaptic surface area and altered active zone topography. Membrane infoldings in otoferlin mutant IHCs indicated disturbed transport of endocytotic membranes and link the above morphological changes to a complementary role of otoferlin and myosin VI in transport of intracellular compartments to the basolateral IHC membrane.