A human homologue of Drosophila kelch associates with myosin-VIIa in specialized adhesion junctions.
Mutations in myosin-VIIa are responsible for the deaf-blindness, Usher disease. Myosin-VIIa is also highly expressed in testis, where it is associated with specialized adhesion plaques termed ectoplasmic specializations (ES) that form between Sertoli cells and germ cells. To identify new roles for myosin-VIIa, we undertook a yeast two-hybrid screen to identify proteins associated with myosin-VIIa in the ES. We identified Keap1, a human homologue of the Drosophila ring canal protein, kelch. The kelch-repeats in the C-terminus of human Keap1 associate with the SH3 domain of myosin-VIIa. Immunolocalization studies revealed that Keap1 is present with myosin-VIIa in the actin bundles of the ES. Myosin-VIIa and Keap1 copurify with ES and colocate with each other and with F-actin at the electron microscopy level. Interestingly, in many epithelial cell types including cells derived from retina and inner ear, Keap1 is a component of focal adhesions and zipper junctions. Keap1 can target to the ES in the absence of myosin-VIIa, suggesting that Keap1 associates with other molecules in the adhesion plaque. Keap1 and myosin-VIIa overlapped in expression in the inner hair cells of the cochlea, suggesting that Keap1 may be a part of a family of actin-binding proteins that could be important for myosin-VIIa function in testis and inner ear.
Velichkova
Michaella
M
Division of Biology, Section of Cell and Developmental Biology, University of California at San Diego, La Jolla 92093, USA.
Guttman
Julian
J
Warren
Carmen
C
Eng
Lily
L
Kline
Katie
K
Vogl
A Wayne
AW
Hasson
Tama
T
D008841:Actin Cytoskeleton / Q000737:chemistry; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003051:Cochlea / Q000737:chemistry / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D004330:Drosophila; D029721:Drosophila Proteins; D004398:Dyneins; D004847:Epithelial Cells; D022001:Focal Adhesions / Q000737:chemistry / Q000378:metabolism*; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism; D006801:Humans; D000072019:Kelch-Like ECH-Associated Protein 1; D008297:Male; D051379:Mice; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D000081412:Myosin VIIa; D009218:Myosins / Q000378:metabolism*; D013737:Testis / Q000737:chemistry / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; C000631455:MYO7A protein, human; D008840:Microfilament Proteins; C000631456:Myo7a protein, mouse; D000081412:Myosin VIIa; C080353:kel protein, Drosophila; C000631458:myosin 7a, Drosophila; D009218:Myosins; D004398:Dyneins