RESUMEN
BACKGROUND: Changes in genes coding for ciliary proteins contribute to complex human syndromes called ciliopathies, such as Bardet-Biedl Syndrome (BBS). We used the model organism Paramecium to focus on ciliary ion channels that affect the beat form and sensory function of motile cilia and evaluate the effects of perturbing BBS proteins on these channels. METHODS: We used immunoprecipitations and mass spectrometry to explore whether Paramecium proteins interact as in mammalian cells. We used RNA interference (RNAi) and swimming behavior assays to examine the effects of BBS depletion on ciliary ion channels that control ciliary beating. Combining RNA interference and epitope tagging, we examined the effects of BBS depletion of BBS 7, 8 and 9 on the location of three channels and a chemoreceptor in cilia. RESULTS: We found 10 orthologs of 8 BBS genes in P. tetraurelia. BBS1, 2, 4, 5, 7, 8 and 9 co-immunoprecipitate. While RNAi reduction of BBS 7 and 9 gene products caused loss and shortening of cilia, RNAi for all BBS genes except BBS2 affected patterns of ciliary motility that are governed by ciliary ion channels. Swimming behavior assays pointed to loss of ciliary K+ channel function. Combining RNAi and epitope tagged ciliary proteins we demonstrated that a calcium activated K+ channel was no longer located in the cilia upon depletion of BBS 7, 8 or 9, consistent with the cells' swimming behavior. The TRPP channel PKD2 was also lost from the cilia. In contrast, the ciliary voltage gated calcium channel was unaffected by BBS depletion, consistent with behavioral assays. The ciliary location of a chemoreceptor for folate was similarly unperturbed by the depletion of BBS 7, 8 or 9. CONCLUSIONS: The co-immunoprecipitation of BBS 1,2,4,5,7,8, and 9 suggests a complex of BBS proteins. RNAi for BBS 7, 8 or 9 gene products causes the selective loss of K+ and PKD2 channels from the cilia while the critical voltage gated calcium channel and a peripheral receptor protein remain undisturbed. These channels govern ciliary beating and sensory function. Importantly, in P. tetraurelia we can combine studies of ciliopathy protein function with behavior and location and control of ciliary channels.
RESUMEN
Neuralized (Neurl) is a highly conserved E3 ubiquitin ligase, which in Drosophila acts upon Notch ligands to regulate Notch pathway signaling. Human Neuralized1 (NEURL1) was investigated as a potential tumor suppressor in medulloblastoma (MB). The gene is located at 10q25.1, a region demonstrating frequent loss of heterozygosity in tumors. In addition, prior publications have shown that the Notch pathway is functional in a proportion of MB tumors and that Neurl1 is only expressed in differentiated cells in the developing cerebellum. In this study, NEURL1 expression was downregulated in MB compared with normal cerebellar tissue, with the lowest levels of expression in hedgehog-activated tumors. Control of gene expression by histone modification was implicated mechanistically; loss of 10q, sequence mutation, and promoter hypermethylation did not play major roles. NEURL1-transfected MB cell lines demonstrated decreased population growth, colony-forming ability, tumor sphere formation, and xenograft growth compared with controls, and a significant increase in apoptosis was seen on cell cycle and cell death analysis. Notch pathway inhibition occurred on the exogenous expression of NEURL1, as shown by decreased expression of the Notch ligand, Jagged1, and the target genes, HES1 and HEY1. From these studies, we conclude that NEURL1 is a candidate tumor suppressor in MB, at least in part through its effects on the Notch pathway.
Asunto(s)
Apoptosis , Neoplasias Cerebelosas/patología , Regulación hacia Abajo , Meduloblastoma/patología , Receptores Notch/genética , Ubiquitina-Proteína Ligasas/fisiología , Adolescente , Adulto , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Western Blotting , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Línea Celular Tumoral , Proliferación Celular , Neoplasias Cerebelosas/genética , Neoplasias Cerebelosas/metabolismo , Cerebelo/metabolismo , Cerebelo/patología , Niño , Preescolar , Metilación de ADN , Proteínas de Drosophila , Epigénesis Genética , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Humanos , Técnicas para Inmunoenzimas , Lactante , Péptidos y Proteínas de Señalización Intercelular/genética , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Proteína Jagged-1 , Meduloblastoma/genética , Meduloblastoma/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Fenotipo , Regiones Promotoras Genéticas/genética , ARN Mensajero/genética , Receptores Notch/antagonistas & inhibidores , Receptores Notch/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteínas Serrate-Jagged , Transducción de Señal , Factor de Transcripción HES-1RESUMEN
We report here the presence of specific plasma membrane calcium pumps (PMCAs) in mouse olfactory sensory neurons. All 4 isoforms are present as shown by deconvolution microscopy, and the specific splice variants are identified by reverse transcriptase (RT)-polymerase chain reaction (PCR). The PMCAs are present on the cell body, dendrite, knob, and cilia, but the different isoforms of PMCAs are not identical in their distributions. The PMCAs are positioned to play a role in calcium clearance after stimulation.