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Keywords
ZNRF1; Tubulin; Ubiquitin; RING finger; Zinc finger
Introduction
The ubiquitin-mediated proteolytic pathway plays an important role in the elimination of short-lived regulatory proteins, including those that contribute to the cell cycle, cellular signaling, secretion, organelle biogenesis, DNA repair, and morphogenesis [1]. Ubiquitin conjugation is catalyzed by PRT 062607 designated as ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin ligase (E3) [2]. E3 is thought to be the component of the ubiquitin conjugation system that is most directly responsible for substrate recognition [1]. On the basis of structural similarity, E3 enzymes have been classified into three families: HECT (homologous to E6-AP COOH terminus) family [3], RING finger-containing protein family [4] and [5] and U-box family [6].
In the nervous system, the ubiquitin–proteasome pathway is thought to play an important role to ensure proper neuronal function including neuritogenesis and neurodegeneration [7] and [8]. Ubiquitin-mediated degradation not only removes misfolded proteins in the subcellular regions of neurons to prevent the development of neurodegenerative diseases but also mediates transduction of intracellular signaling. It has been reported that neurite outgrowth was induced by proteasome inhibitors, suggesting that neurite outgrowth requires an enhanced pool of ubiquitinated proteins or ubiquitin-dependent proteolysis of a negative regulator of neurite outgrowth in vitro [8].