Akiko Miyara et al. (2007) International Worm Meeting "Studies on neuronal function of a novel and conserved protein TTX-8."

Akiko Miyara, Masatoshi Okumura, Yoshifumi Okochi, Ikue Mori, Akane Ohta, Ryo Takano, Atsushi Kuhara

[International Worm Meeting, 2007]

C. elegans can respond to various environmental stimuli including temperature. If we cultivate them at some temperature with food and move them to the thermal gradient, they migrate to the cultivation temperature to find the food. This behavior is called thermotaxis. Several neurons and genes required for thermotaxis have been identified, but molecular mechanism of thermotaxis is still poorly understood. The ttx-8(nj21) and ttx-8(nj34) mutants are defective in thermotaxis and partially defective in chemotaxis. We found that ttx-8 is expressed in many neurons and TTX-8 functions in neurons including AFD, AIY and AIZ neurons responsible for thermotaxis. TTX-8 seems to have several transmembrane domains in the amino terminus and coiled-coil domains in the carboxyl terminus. RIC-3, first identified in C. elegans and conserved among several species, also has transmembrane domains and coiled-coil domains as well (Halevi et al., 2002; Halevi et al., 2003). Since RIC-3 is thought to be required for the maturation of acetylcoline receptor (Halevi et al., 2002), TTX-8 may play a similar role such as folding, assembly, transmission or anchoring of some membrane protein. In fact, our results so far indicate that TTX-8 is localized to peri-nuclei region of cytoplasm, perhaps to some kind of organelle like ER or Golgi-body. Now we are investigating in detail using organelle markers. There seems to be several homologues of TTX-8 in other species. One of them is FLJ10747, a novel protein in human. The introduction of full length FLJ10747 cDNA led to weak but apparent rescue of abnormal thermotaxis phenotype of ttx-8, suggesting that FLJ10747 plays a similar role to TTX-8. We found that TTX-8 may interact with Y11D7A.12, a novel protein with a FLYWCH zinc finger domain, by Yeast two-hybrid screening. The tm2118, deletion mutant of Y11D7A.12, showed almost normal thermotaxis behavior. Now we are trying to isolate the deletion mutant, in which the FLYWCH domain is completely deleted. Also, we are in the process of looking for the other protein that interacts with TTX-8 by two-hybrid screening. We believe that the further analysis of ttx-8 in C. elegans would give us new information about the function of this protein, conserved from nematode to mammals.

Takano, Syuichi et al. (2009) International Worm Meeting "Regulation of protein homeostasis genes is required for long-term survival at cool temperatures."

Larsen, Pamela, Sanchez, Angela, Takano, Syuichi

[International Worm Meeting, 2009]

Animals have adapted to survive ambient temperature fluctuations in their environment. Animals living in cool or warm conditions display physiological responses to the temperature. Two examples are the increase metabolic rate with increased temperature and the increase life span with decreased temperature. Generally, it is believed that these physiological changes are due to thermodynamic effects. We have found that the temperature-dependent changes in metabolic rate and life span are mutable. Certain mutant daf-2 alleles are abnormal for an increased of metabolic rate with increased temperature or for a decreased of life span with increased temperature. We are interested in understanding the biological mechanisms triggered by a cool or warm temperature shift and whether the biological responses contribute to the enhanced or reduced survival for the individual living in the new climate. In the laboratory, cultivation temperatures from 15 deg C to 25 deg C are used for C. elegans. We found significant differential expression of 338 genes in a microarray analysis of worms acclimatized to 15 deg C or 25 deg C (unpublished S. Takano, C. Curtis, S. Tavare and P. L. Larsen). Among these genes the categories of protein synthesis and proteolysis were over-represented, suggesting protein homeostasis is critical to temperature acclimatization. Quantitative RT-PCR was used to establish that differential expression does occur for specific genes related to protein synthesis and proteases. The steady-state expression level is higher at 15 deg C than 25 deg C. This result is counterintuitive as the expectation had been that cellular processes are generally higher at 25 deg C, yet this is not the case for the more than 30 genes related to protein synthesis or proteolysis tested. There are hundreds of genes in the genome in these two categories and the majority of these genes are not differentially expressed. The apparent specificity of the temperature-dependent regulation raised the possibility that an increase of protein synthesis and particular proteolysis contributes to the enhanced long-term survival at the cool temperature. To test this, adult worms cultivated at 15 deg C were fed RNAi E. coli of the protein-homeostasis-related genes. The knockdown of some of these genes caused severe herniation while others caused paralysis. This suggests that while thermodynamics may play a role in enhanced long-term survival in cool conditions, it is not sufficient. The regulation of specific protein synthesis-related and proteolysis genes is necessary for healthy long-term survival in cool conditions.