RESUMEN
The honeybee is a model system to study learning and memory, and Ca(2+) signals play a key role in these processes. We have cloned, expressed, and characterized the first honeybee Ca(2+) channel subunit. We identified two splice variants of the Apis CaVß Ca(2+) channel subunit (Am-CaVß) and demonstrated expression in muscle and neurons. Although AmCaVß shares with vertebrate CaVß subunits the SH3 and GK domains, it beholds a unique N terminus that is alternatively spliced in the first exon to produce a long (a) and short (b) variant. When expressed with the CaV2 channels both, AmCaVßa and AmCaVßb, increase current amplitude, shift the voltage-sensitivity of the channel, and slow channel inactivation as the vertebrate CaVß2a subunit does. However, as opposed to CaVß2a, slow inactivation induced by Am-CaVßa was insensitive to palmitoylation but displayed a unique PI3K sensitivity. Inactivation produced by the b variant was PI3K-insensitive but staurosporine/H89-sensitive. Deletion of the first exon suppressed the sensitivity to PI3K inhibitors, staurosporine, or H89. Recording of Ba(2+) currents in Apis neurons or muscle cells evidenced a sensitivity to PI3K inhibitors and H89, suggesting that both AmCaVß variants may be important to couple cell signaling to Ca(2+) entry in vivo. Functional interactions with phospho-inositide and identification of phosphorylation sites in AmCaVßa and AmCaVßb N termini, respectively, suggest that AmCaVß splicing promoted two novel and alternative modes of regulation of channel activity with specific signaling pathways. This is the first description of a splicing-dependent kinase switch in the regulation of Ca(2+) channel activity by CaVß subunit.
Asunto(s)
Potenciales de Acción , Abejas/metabolismo , Canales de Calcio/metabolismo , Proteínas de Insectos/metabolismo , Empalme Alternativo , Secuencia de Aminoácidos , Animales , Abejas/química , Abejas/genética , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio/química , Canales de Calcio/genética , Células Cultivadas , Exones , Eliminación de Gen , Células HEK293 , Humanos , Proteínas de Insectos/química , Proteínas de Insectos/genética , Datos de Secuencia Molecular , Fibras Musculares Esqueléticas/fisiología , Neuronas/fisiología , Fosfatidilinositol 3-Quinasas/farmacología , Inhibidores de las Quinasa Fosfoinosítidos-3 , Fosforilación , Inhibidores de Proteínas Quinasas/farmacología , Estructura Terciaria de Proteína , Subunidades de Proteína/química , Subunidades de Proteína/genética , Subunidades de Proteína/metabolismo , XenopusRESUMEN
Innate immunity plays a critical role in the host response to a viral infection. In particular, type I interferons (IFN-I) are major effectors of antiviral innate immunity. Herein, interplays between HTLV-1 and the IFN-I response are reviewed. Particular emphasis is put on virus sensing by innate immunity receptors and on anti-HTLV-1 effects of IFN-I. We also discuss HTLV-1-induced alteration of IFN-I function and how IFN-I/AZT treatment of adult T-cell leukemia/lymphoma patients can lead to complete remission despite virus-induced escape mechanisms.
