Molecular & behavioral analysis of TRP channel pyrexia and atlastin

Abstract

Recently, several transient receptor potential (TRP) channels were found to be activated by temperature stimuli in vitro. However, their physiological and behavioural roles are largely unknown. From a temperature preference behaviour screen of 27,000 Drosophila P-insertion mutants, we isolated a novel TRP channel gene, named pyrexia (pyx). Pyx was opened by temperatures above 40$^\circ$C in Xenopus oocytes and HEK293T cells. It was ubiquitously expressed along the dendrites of subset of PNS neurons and more permeable to $K^+$ than $Na^+$. Although some pyx alleles showed abnormal temperature-preferences, the pyx null flies surprisingly did not show temperature-preference statistically different from wild-type. However, 60% of pyx null flies were paralyzed within 3 minutes upon exposure to 40$^\circ$C while only 9% of wild-type were paralyzed by the same stimulus. From these findings we propose that the primary in vivo role of Pyx is to protect Drosophila from high temperature stress. Meanwhile, the early onset hereditary spastic paraplegia (HSP) SPG3A is caused in the mutations in the atlastin gene, which encodes a GTPase. HSP appears to selectively affect the distal regions of the longest axons within the spinal cord. To date, understanding of the cellular and molecular mechanisms responsible for this disorder is unknown. So we isolated an EP-insertion mutant animal, which is adult viable, but sterile and has small body size. The atlastin null adult flies have severe impairment in movement and short life span. We showed that these severe movement defects were caused by dopaminergic neuronal degeneration as the age-dependent manner. In addition, we analyzed the function of atlastin in oogenesis. ATL showed the very specific localization to the oocyte temporally and spatially. The loss-of-function study provides that atlastin is essential for the oocyte fate maintenance. Together, these findings indicate that the Drosophila atlastin is necessary for the nor...