Ubiquilin-1 (Ubqln1 or Ubqln), a ubiquitin-like protein, mediates degradation of misfolded proteins and has been implicated in a number of pathological and physiological conditions. To better understand its function in vivo, we recently generated transgenic (Tg) mice that globally overexpress mouse Ubqln in a variety of tissues and ubqln conditional knock-out mice. The Tg mice were viable and did not show any developmental or behavioral abnormalities compared with their wild-type (WT) littermates. When subjected to oxidative stress or ischemia/reperfusion, however, ubqln Tg mice but not theWTlittermates showed increased tolerance to these insults. Following ischemic stroke, ubqln Tg mice recovered motor function more rapidly than did the WT mice. In contrast, KO of ubqln exacerbated neuronal damage after stroke. In addition, KO of ubqln also caused accumulation of ubiquitinated proteins. When ubqln KO mice were crossed with a ubiquitin-proteasome system function reporter mouse, the accumulation of a proteasome surrogate substrate was observed. These results suggest that Ubqln protects mice from oxidative stress and ischemic stroke-caused neuronal injury through facilitating removal of damaged proteins. Thus, enhanced removal of unwanted proteins is a potential therapeutic strategy for treating stroke-caused neuronal injury.
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