RT Journal Article SR Electronic T1 Rapid Turnover of Stereocilia Membrane Proteins: Evidence from the Trafficking and Mobility of Plasma Membrane Ca2+-ATPase 2 JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 6386 OP 6395 DO 10.1523/JNEUROSCI.1215-06.2006 VO 26 IS 23 A1 M’hamed Grati A1 Mark E. Schneider A1 Karen Lipkow A1 Emanuel E. Strehler A1 Robert J. Wenthold A1 Bechara Kachar YR 2006 UL http://www.jneurosci.org/content/26/23/6386.abstract AB We studied the spatial distribution, mobility, and trafficking of plasma membrane Ca2+ATPase-2 (PMCA2), a protein enriched in the hair cell apical membrane and essential for hair cell function. Using immunofluorescence, we determined that PMCA2 is enriched in the stereocilia and present at a relatively low concentration in the kinocilium and in the remaining apical membrane. Using an antibody to the extracellular domain of PMCA2 as a probe, we observed that PMCA2 diffuses laterally from the stereocilia membrane and is internalized at the apical cell border maintaining an estimated half-life of residency in the stereocilia of ∼5–7 h. A computer simulation of our data indicates that PMCA2 has an estimated global diffusion coefficient of 0.01–0.005 μm2/s. Using a green fluorescent protein tag, we observed that PMCA2 is rapidly delivered to the apical cell border from where it diffuses to the entire stereocilia surface. Fluorescence recovery after photobleaching experiments show that ∼60% of PMCA2 in the stereocilia exhibit high mobility with a diffusion coefficient of 0.1–0.2 μm2/s, whereas the remaining pool represents a relatively immobile fraction. These results suggest that PMCA2 molecules maintain transient interactions with other components of the stereocilia, and the mobile pool of PMCA2 mediates the exchange between the stereocilia and the removal and delivery sites at the periphery of the apical cell surface. This rapid turnover of a major stereocilia membrane protein matches the previously described rapid turnover of proteins of the stereocilia actin core, further demonstrating that these organelles undergo rapid continuous renewal.