RESUMEN
Presenilins are components of the gamma-secretase protein complex that mediates intramembranous cleavage of betaAPP and Notch proteins. A C. elegans genetic screen revealed two genes, aph-1 and pen-2, encoding multipass transmembrane proteins, that interact strongly with sel-12/presenilin and aph-2/nicastrin. Human aph-1 and pen-2 partially rescue the C. elegans mutant phenotypes, demonstrating conserved functions. The human genes must be provided together to rescue the mutant phenotypes, and the inclusion of presenilin-1 improves rescue, suggesting that they interact closely with each other and with presenilin. RNAi-mediated inactivation of aph-1, pen-2, or nicastrin in cultured Drosophila cells reduces gamma-secretase cleavage of betaAPP and Notch substrates and reduces the levels of processed presenilin. aph-1 and pen-2, like nicastrin, are required for the activity and accumulation of gamma-secretase.
Asunto(s)
Precursor de Proteína beta-Amiloide/metabolismo , Proteínas de Caenorhabditis elegans/aislamiento & purificación , Membrana Celular/metabolismo , Endopeptidasas/metabolismo , Proteínas de Homeodominio/aislamiento & purificación , Proteínas de la Membrana/aislamiento & purificación , Proteínas de la Membrana/metabolismo , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Secretasas de la Proteína Precursora del Amiloide , Precursor de Proteína beta-Amiloide/genética , Animales , Ácido Aspártico Endopeptidasas , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Membrana Celular/ultraestructura , Células Cultivadas , Clonación Molecular , Proteínas de Drosophila , Drosophila melanogaster , Elementos de Facilitación Genéticos/genética , Glucagón/metabolismo , Péptido 1 Similar al Glucagón , Proteínas del Helminto/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Humanos , Membranas Intracelulares/metabolismo , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Mutación/genética , Fragmentos de Péptidos/metabolismo , Presenilina-1 , Precursores de Proteínas/metabolismo , Receptores Notch , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Transducción de Señal/genéticaRESUMEN
In C. elegans, cells of the QL and QR neuroblast lineages migrate with left-right asymmetry; QL and its descendants migrate posteriorly whereas QR and its descendants migrate anteriorly. One key step in generating this asymmetry is the expression of the Hox gene mab-5 in the QL descendants but not in the QR descendants. This asymmetry appears to be coupled to the asymmetric polarizations and movements of QL and QR as they migrate and relies on an asymmetric response to an EGL-20/Wnt signal. To identify genes involved in these complex layers of regulation and to isolate targets of mab-5 that direct posterior migrations, we screened visually for mutants with cell migration defects in the QL and QR lineages. Here, we describe a set of new mutants (qid-5, qid-6, qid-7, and qid-8) that primarily disrupt the migrations of the QL descendants. Most of these mutants were defective in mab-5 expression in the QL lineage and might identify genes that interact directly or indirectly with the EGL-20/Wnt signaling pathway.
Asunto(s)
Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Movimiento Celular , Genes de Helminto , Neuronas/metabolismo , Alelos , Animales , Animales Modificados Genéticamente , Tipificación del Cuerpo/genética , Caenorhabditis elegans/citología , Caenorhabditis elegans/efectos de los fármacos , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Linaje de la Célula , Metanosulfonato de Etilo/farmacología , Regulación del Desarrollo de la Expresión Génica , Genes Homeobox , Glicoproteínas/genética , Glicoproteínas/metabolismo , Proteínas del Helminto/genética , Proteínas del Helminto/metabolismo , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Modelos Genéticos , Mutagénesis , Mutágenos/farmacología , Mutación , Neuronas/citología , Transducción de Señal , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transgenes , Proteínas WntRESUMEN
Anteroposterior cell migration and patterning in C. elegans are governed by multiple, interacting signaling pathways and transcription factors. In this study, we have investigated the role of ceh-20, the C. elegans ortholog of the HOX co-factor Extradenticle (Exd/Pbx), and unc-62, the C. elegans ortholog of Homothorax (Hth/Meis/Prep), in two processes that are regulated by Hox gene lin-39: cell migration and vulva formation. As in lin-39 mutants, the anterior migrations of neuroblasts in the Q lineage are truncated in Hox co-factor mutants. Surprisingly, though, our findings suggested that the roles of ceh-20 and unc-62 are different from that of lin-39; specifically, ceh-20 and unc-62 but not lin-39 are required for the transmembrane protein MIG-13 to promote anterior migration. To our knowledge, ceh-20 and unc-62 are the only genes that have been implicated in the mig-13 pathway. We find that ceh-20 and unc-62 are also required for several steps in vulva development. Surprisingly, ceh-20 and unc-62 mutants have phenotypes that are starkly different from those of lin-39 mutants. Thus, in this process, too, ceh-20 and unc-62 are likely to have functions that are independent of lin-39.