Krzysztof Drabikowski et al. (2003) International Worm Meeting "Intracellular domain of Ten-1 is released from the membrane and signals directly to the nucleus."

Krzysztof Drabikowski, Ruth Chiquet-Ehrismann, Jacqueline Ferralli

[International Worm Meeting, 2003]

The ten-m gene was identified in Drosophila as the first pair rule gene that is not a transcription factor but a cell surface protein. In addition to the early embryonic expression it is also expressed in the developing nervous system of the fly. Members of the Ten-m protein family were also identified in vertebrates and have been named teneurins. Vertebrate teneurins are highly expressed in developing tissues especially in the nervous system. Members of the Ten family are type II transmembrane proteins. The N-terminal, intracellular part is followed by a single transmembrane domain. The extracellular domain is around 2500 aa and contains EGF-like repeats. The C. elegans ten-1 is located on chromosome III and is mapped to the cosmid R13F6. By 5'-RACE analysis we identified an alternative transcription start located 8 kb upstream of the predicted one. Both ten-1 forms are expressed early in C. elegans morphogenesis. In post-embryonic development the protein from the upstream promoter is expressed in the developing somatic gonad, the pharynx, vulva and body wall muscles and a subset of neurons. It is also expressed in the germ line, both in developing oocytes and sperm. The protein from the downstream promoter in adult worms has a broad neuronal expression. RNAi aimed against ten-1 transcripts affects worm morphogenesis in various stages of development. Embryos die because of elongation defects. Variably abnormal larvae develop. Adult worms show defects in gonad migration. Worms have little or no sperm. Sperm is often pushed to the uterus by ovulating oocytes. Ovulation is defective resulting in ruptured oocytes and abnormally small embryos. Endomitotic oocytes form in the uterus. Worms are constipated. We have developed antibodies against the N- and C-terminal peptides of the Ten-1 protein. The anti C-terminus stains the cell membranes but the anti N-terminus antibody stains cell membranes as well as the nuclei. This suggests the release of the intracellular domain from the membrane and translocation to the nucleus. The Ten-1 nuclear staining is reminiscent of the PML nuclear bodies in vertebrates. We postulate that Ten-1 is a receptor for a morphogenetic cue and its intracellular domain is a membrane bound transcription regulator that signals directly from the membrane to the nucleus.

Krzysztof Drabikowski et al. (2005) International Worm Meeting "Global approach to sumoylation in C. elegans."

Jacqueline Ferralli, Ruth Chiquet-Ehrismann, Krzysztof Drabikowski, Ralf Baumeister

[International Worm Meeting, 2005]

Small ubiquitin-related modifier (SUMO) proteins are covalently and reversibly coupled to several intracellular protein targets modulating protein-protein and protein-DNA interactions. Despite rapid progress, key questions about the regulation mechanisms remain to be answered. Is there a SUMO receptor? Where does sumoylation specificity come from and what are the signaling events regulating the timing of SUMO ligation and de-sumoylation? Several SUMO targets belong to signaling pathways involved in cancer and neurodegenerative diseases. SUMO attachment to target proteins affects their function and stability and might be used as a therapeutic target. For example, arsenite is used as a treatment for a certain type of promyelotic leukemia and is acting by specific induction of sumoylation of PML and PMLretinoic acid receptor fusion protein. Enhanced sumoylation of these proteins leads to apoptosis of malignant cells. In the Drosophila model of Huntington disease it was shown that SUMO competes with ubiquitin for the same attachment site. Attachment of SUMO to the pathogenic fragment of huntingtin protein protects it from ubiquitination and degradation and thereby enhancing neurodegeneration. We decided to study the sumoylation process at the level of the entire organism using C. elegans as a model system. Establishing the complete list of SUMO targets is the first step to decipher the pathways regulated by SUMO. Our estimates suggest that the expected number of proteins undergoing sumoylation is 200 in yeast and worms and 600 proteins in humans and mice. Identification of SUMO targets in C. elegans is performed by purification of sumoylated proteins from transgenic worms expressing a tagged form of SUMO. The purified proteins are identified by mass spectrometric analysis. It has been proposed that part of the sumoylation specificity and dynamics is regulated by different de-sumoylating enzymes. In the C. elegans genome there are 6 genes, encoding proteins containing the SUMO protease domain. We performed knock-down experiments of these genes using RNA interference. We have identified the protease responsible for maturation of SUMO by cleaving of the C-terminus. Five other proteases show important differences in the global sumoylation pattern in the worm upon treatment. Manipulating protein activity by affecting their sumoylation state might be a target for therapeutic intervention and studies in C. elegans can help to establish the basic knowledge of sumoylation processes as well as to screen for potential drugs.