RESUMEN
Phosphatidylinositol phosphate kinase type 1γ (PIPKIγ) is a key enzyme in the generation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] and is expressed at high levels in the nervous system. Homozygous knockout mice lacking this enzyme die postnatally within 24 h, whereas PIPKIγ(+/-) siblings breed normally and have no reported phenotype. Here we show that adult PIPKIγ(+/-) mice have dramatically elevated hearing thresholds for high-frequency sounds. During the first postnatal week we observed a reduction of ATP-dependent Ca(2+) signaling activity in cochlear nonsensory cells. Because Ca(2+) signaling under these conditions depends on inositol-1,4,5-trisphosphate generation from phospholipase C (PLC)-dependent hydrolysis of PI(4,5)P(2), we conclude that (i) PIPKIγ is primarily responsible for the synthesis of the receptor-regulated PLC-sensitive PI(4,5)P(2) pool in the cell syncytia that supports auditory hair cells; (ii) spatially graded impairment of this signaling pathway in cochlear nonsensory cells causes a selective alteration in the acquisition of hearing in PIPKIγ(+/-) mice. This mouse model also suggests that PIPKIγ may determine the level of gap junction contribution to cochlear development.
Asunto(s)
Señalización del Calcio/fisiología , Sordera/genética , Sordera/metabolismo , Órgano Espiral/metabolismo , Fosfatidilinositol 4,5-Difosfato/metabolismo , Fosfotransferasas (Aceptor de Grupo Alcohol)/genética , Factores de Edad , Animales , Animales Recién Nacidos , Conexinas/genética , Conexinas/metabolismo , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Uniones Comunicantes/metabolismo , Células Ciliadas Auditivas/metabolismo , Audición/fisiología , Mecanotransducción Celular/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , FN-kappa B/metabolismo , Órgano Espiral/crecimiento & desarrollo , Fenotipo , Fosfotransferasas (Aceptor de Grupo Alcohol)/metabolismo , Percepción de la Altura Tonal/fisiologíaRESUMEN
One challenge in biology is signal transduction monitoring in a physiological context. Intravital imaging techniques are revolutionizing our understanding of tumor and host cell behaviors in the tumor environment. However, these deep tissue imaging techniques have not yet been adopted to investigate the second messenger calcium (Ca²âº). In the present study, we established conditions that allow the in vivo detection of Ca²âº signaling in three-dimensional tumor masses in mouse models. By combining intravital imaging and a skinfold chamber technique, we determined the ability of photodynamic cancer therapy to induce an increase in intracellular Ca²âº concentrations and, consequently, an increase in cell death in a p53-dependent pathway.