TY - JOUR
T1 - Large membrane domains in hair bundles specify spatially constricted radixin activation
AU - Zhao, Hongyu
AU - Williams, Diane E.
AU - Shin, Jung Bum
AU - Brügger, Britta
AU - Gillespie, Peter G.
PY - 2012/3/28
Y1 - 2012/3/28
N2 - The plasma membrane of vertebrate hair bundles interacts intimately with the bundle cytoskeleton to support mechanotransduction and homeostasis. To determine the membrane composition of bundles, we used lipid mass spectrometry with purified chick vestibular bundles. While the bundle glycerophospholipids and acyl chains resemble those of other endomembranes, bundle ceramide and sphingomyelin nearly exclusively contain short-chain, saturated acyl chains. Confocal imaging of isolated bullfrog vestibular hair cells shows that the bundle membrane segregates spatially into at least three large structural and functional domains. One membrane domain, including the stereocilia basal tapers and ~1μm of the shaft, the location of the ankle links, is enriched in the lipid phosphatase PTPRQ (protein tyrosine phosphatase Q) and polysialylated gangliosides. The taper domain forms a sharp boundary with the shaft domain, which contains the plasma membrane Ca 2+-ATPase isoform 2 (PMCA2) and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2]; moreover, a tip domain has elevated levels of cholesterol, PMCA2, and PI(4,5)P 2. Protein mass spectrometry shows that bundles from chick vestibular hair cells contain a complete set of proteins that transport, synthesize, and degrade PI(4,5)P 2. The membrane domains have functional significance; radixin, essential for hair-bundle stability, is activated at the taper-shaft boundary in a PI(4,5)P 2-dependent manner, allowing assembly of protein complexes at that site. Membrane domains within stereocilia thus define regions within hair bundles that allow compartmentalization of Ca 2+ extrusion and assembly of protein complexes at discrete locations.
AB - The plasma membrane of vertebrate hair bundles interacts intimately with the bundle cytoskeleton to support mechanotransduction and homeostasis. To determine the membrane composition of bundles, we used lipid mass spectrometry with purified chick vestibular bundles. While the bundle glycerophospholipids and acyl chains resemble those of other endomembranes, bundle ceramide and sphingomyelin nearly exclusively contain short-chain, saturated acyl chains. Confocal imaging of isolated bullfrog vestibular hair cells shows that the bundle membrane segregates spatially into at least three large structural and functional domains. One membrane domain, including the stereocilia basal tapers and ~1μm of the shaft, the location of the ankle links, is enriched in the lipid phosphatase PTPRQ (protein tyrosine phosphatase Q) and polysialylated gangliosides. The taper domain forms a sharp boundary with the shaft domain, which contains the plasma membrane Ca 2+-ATPase isoform 2 (PMCA2) and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P 2]; moreover, a tip domain has elevated levels of cholesterol, PMCA2, and PI(4,5)P 2. Protein mass spectrometry shows that bundles from chick vestibular hair cells contain a complete set of proteins that transport, synthesize, and degrade PI(4,5)P 2. The membrane domains have functional significance; radixin, essential for hair-bundle stability, is activated at the taper-shaft boundary in a PI(4,5)P 2-dependent manner, allowing assembly of protein complexes at that site. Membrane domains within stereocilia thus define regions within hair bundles that allow compartmentalization of Ca 2+ extrusion and assembly of protein complexes at discrete locations.
UR - http://www.scopus.com/inward/record.url?scp=84859090163&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84859090163&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.6184-11.2012
DO - 10.1523/JNEUROSCI.6184-11.2012
M3 - Article
C2 - 22457506
AN - SCOPUS:84859090163
SN - 0270-6474
VL - 32
SP - 4600
EP - 4609
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 13
ER -