Chronic hypoxia stress-induced differential modulation of heat-shock protein 70 and presynaptic proteins.
Chronic hypoxia exposure can cause neurobehavioral dysfunction, but the underlying cellular and molecular mechanisms remain unclear. Here, we found that adult Lymnaea stagnalis snails maintained in low O(2) (approximately 5%) for 4 days developed slowed reactions to light stimuli, and reduced righting movement. Semiquantitative immunoblotting analyses showed that hypoxia exposure induced increased expression of heat-shock protein (HSP)70 in ganglion preparations, and suppressed expression of the presynaptic proteins syntaxin I, synaptic vesicle protein 2 (SV2) and synaptotagmin I. Detailed time course analyses showed that an early moderate increase developed within 6 h, preceding a substantial up-regulation of HSP70 after 4 days; an early reduction of syntaxin I in the first 24 h; a delayed reduction of synaptotagmin I after 4 days; and a biphasic change in SV2. Using a double-stranded RNA interference approach, we demonstrated that preventing the hypoxia inducible HSP70 enhanced down-regulation of syntaxin and synaptotagmin, and aggravated motor and sensory suppression. Co-immunoprecipitation analysis revealed an interaction between HSP70 and syntaxin. We have thus provided the first evidence that early induction of HSP70 by chronic hypoxia is critical for maintaining expression levels of presynaptic proteins. These findings implicate a new molecular mechanism underlying chronic hypoxia-induced neurobehavioral adaptation and impairment.
Fei
Guanghe
G
Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
Guo
Conghui
C
Sun
Hong-Shuo
HS
Feng
Zhong-Ping
ZP
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D015153:Blotting, Western / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D047468:Immunoprecipitation / Q000379:methods; D008195:Lymnaea; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D012330:RNA, Double-Stranded / Q000008:administration & dosage; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors
D018840:HSP70 Heat-Shock Proteins; D009419:Nerve Tissue Proteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger