Differential distribution of beta- and gamma-actin in guinea-pig cochlear sensory and supporting cells.
Sensory and supporting cells of the mammalian organ of Corti have cytoskeletons containing beta- and gamma-actin isoforms which have been described as having differing intracellular distributions in chick cochlear hair cells. Here, we have used post-embedding immunogold labelling for beta- and gamma-actin to investigate semiquantitatively how they are distributed in the guinea-pig cochlea and to compare different frequency locations. Amounts of beta-actin decrease and gamma-actin increase in the order, outer pillar cells, inner pillar cells, Deiters' cells and hair cells. There is also more beta-actin and less gamma-actin in outer pillar cells in higher than lower frequency regions. In hair cells, beta-actin is present in the cuticular plate but is more concentrated in the stereocilia, especially in the rootlets and towards the periphery of their shafts; labelling densities for gamma-actin differ less between these locations and it is the predominant isoform of the hair-cell lateral wall. Alignments of immunogold particles suggest beta-actin and gamma-actin form homomeric filaments. These data confirm differential distribution of these actin isoforms in the mammalian cochlea and reveal systematic differences between sensory and supporting cells. Increased expression of beta-actin in outer pillar cells towards the cochlear base may contribute to the greater stiffness of this region.
Furness
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MacKay Institute of Communication and Neuroscience, School of Life Sciences, Keele University, Staffordshire ST5 5BG, United Kingdom. coa14@keele.ac.uk
Katori
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Y
Mahendrasingam
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S
Hackney
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CM
D000199:Actins / Q000378:metabolism*; D000818:Animals; D003051:Cochlea / Q000166:cytology / Q000294:innervation / Q000378:metabolism*; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D020033:Protein Isoforms / Q000378:metabolism; D014018:Tissue Distribution
D000199:Actins; D020033:Protein Isoforms