title: Hypo-osmotic shock induces nuclear export and proteasome-dependent decrease of UBL5.
abstract: The osmolarity of body fluid is strictly controlled through the action of diuretic hormones, which are secreted in the hypothalamus. In the mammalian brain, ubiquitin-like 5 (UBL5) is expressed in oxytocin- and vasopressin-positive neurons in the hypothalamus, and these neurons play a role in regulating osmolarity. We examined the dynamics of UBL5 levels in response to hyper- or hypo-osmotic conditions. Hypo-osmotic conditions led to significantly reduced levels of UBL5 both in brain slices from the hypothalamus and in NIH-3T3 cells. This decrease in UBL5 was transcription-independent and proteasome-dependent. Time-course immunocytochemical studies using exogenous UBL5 revealed that the protein was exported from the nucleus under hypo-osmotic conditions and decreased in a proteasome-dependent manner. This report is the first to describe changes in the intracellular and subcellular localization of UBL5 in response to hypo-osmotic conditions. Our results imply osmoregulation of UBL5.
authors.affiliation: Mitsubishi Kagaku Institute of Life Sciences (MITILS), Machida, Tokyo 194-8511 Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Hatanaka
authors.forename: Koji
authors.initials: K
authors.lastname: Ikegami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takagi
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Setou
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D015536:Down-Regulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009997:Osmotic Pressure; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D014452:Ubiquitins
chemical_list: D009419:Nerve Tissue Proteins; D014452:Ubiquitins; C485936:Ubl5 protein, mouse; D046988:Proteasome Endopeptidase Complex