Otoferlin interacts with myosin VI: implications for maintenance of the basolateral synaptic structure of the inner hair cell.
Otoferlin has been proposed to be the Ca(2+) 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 Ca(V)1.3 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 Ca(2+) 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.
University of Tübingen, Institute of Human Genetics, Wilhelmstr. 27, 72074 Tübingen, Germany.
Paulina
P
Heidrych
Ulrike
U
Zimmermann
Stephanie
S
Kuhn
Christoph
C
Franz
Jutta
J
Engel
Susanne V
SV
Duncker
Bernhard
B
Hirt
Carsten M
CM
Pusch
Peter
P
Ruth
Markus
M
Pfister
Walter
W
Marcotti
Nikolaus
N
Blin
Marlies
M
Knipper
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003638:Deafness / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005089:Exocytosis; D006199:Hair Cells, Auditory, Inner / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D013569:Synapses / Q000737:chemistry* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D008565:Membrane Proteins; C089785:myosin VI; C516233:otoferlin protein, mouse; D018995:Myosin Heavy Chains; D002118:Calcium