The adhesive disc in the mobilid ciliate Trichodina pediculus: evidence for centrin-related, calcium-sensitive filaments.

International audienceThe adhesive disc is a highly complex apparatus that allows mobilid ciliates to attach to the tissues of a variety of aquatic invertebrates and vertebrates. The disc comprises concentric rings of rigid skeletal pieces interconnected by filamentous material. This study explored the biochemical properties of the filamentous disc material in the trichodinid Trichodina pediculus. Calcium sensitivity of this material was suggested in vitro by the appearance of transverse cross-striation along bundles of filaments following calcium shock, and complete solubilization of the filamentous material in the presence of EGTA. A 23-kDa immunoanalog of centrins was immunoprecipitated from the EGTA extract. The protein binds calcium as indicated by (45) Ca(2+) blot overlay and Ca(2+) -induced shifts in electrophoretic mobility. Using Ca(2+) /EGTA buffers, we demonstrated a direct relationship between extraction of the filaments and solubilization of the protein. Immunofluorescence and immunoelectron microscopy confirmed that the protein localized to the filamentous disc material and revealed cross-reactivity with the spasmoneme, which is the prototype of ion-sensitive, centrin-like contractile systems in ciliates. The possibility that the filamentous disc material may be a novel example of Ca(2+) -sensitive, centrin-based systems found in ciliates is discussed

A BAD link to mitochondrial cell death in the cochlea of mice with noise-induced hearing loss

Acoustic overstimulation induces calcium overload and activation of mitochondria-mediated cell death pathways in outer hair cells (OHC) of the cochlea. However, it is not known whether these events are interrelated or independent. We have recently reported that the calcium-dependent phosphatase calcineurin is activated in OHC following noise exposure and now postulate that calcium overload triggers mitochondria-mediated death pathways through activation of Bcl-2-associated death promoter (BAD) by calcineurin. CBA/J mice were exposed to broadband noise (2–20 kHz), causing a permanent threshold shift of about 40 dB at 12 and 20 kHz, corresponding to damage in the middle and basal turns of the cochlea. Loss of OHC in the basal region was evident in surface preparations. BAD immunostaining in control animals had a cytoplasmic distribution in the cells of the organ of Corti. Five hours after acoustic overstimulation, mitochondria and BAD redistributed to the perinuclear region of OHC in the basal and middle turns but not in the apical turn. The nonapoptotic phospho-BAD (Ser 112) was up-regulated in cells undamaged by noise (supporting cells and inner hair cells) but not in OHC. These data establish a connection between calcium overload and mitochondria-mediated death pathways in OHC and also suggest a dual role for BAD. The translocation of BAD to the mitochondria in degenerating cells is indicative of the activation of its proapoptotic capacity, whereas up-regulation of phospho-BAD is consistent with a nonapoptotic role of BAD in less vulnerable cells. © 2006 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49294/1/2535_ftp.pd