Functional regulation of FEZ1 by the U-box-type ubiquitin ligase E4B contributes to neuritogenesis.
E4B (also known as UFD2a) is a mammalian homolog of Saccharomyces cerevisiae Ufd2, which was originally described as a ubiquitin chain assembly factor (E4). E4B is a U-box-type ubiquitin-protein isopeptide ligase (E3) and likely functions as either an E3 or an E4. With a yeast two-hybrid screen, we have now identified FEZ1 (fasciculation and elongation protein zeta 1) as a protein that interacts with E4B. FEZ1 is implicated in neuritogenesis when phosphorylated by protein kinase Czeta (PKCzeta). Interaction between E4B and FEZ1 in mammalian cells was enhanced by coexpression of constitutively active PKCzeta. E4B mediated the polyubiquitylation of FEZ1 but did not affect its intracellular stability, suggesting that such modification of FEZ1 is not a signal for its proteolysis. Polyubiquitylation of FEZ1 by E4B required Lys(27) of ubiquitin. Expression of a dominant-negative mutant of E4B in rat pheochromocytoma PC12 cells resulted in inhibition of neurite extension induced either by nerve growth factor or by coexpression of FEZ1 and constitutively active PKCzeta. These findings indicate that E4B serves as a ubiquitin ligase for FEZ1 and thereby regulates its function but not its degradation.
Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Fumihiko
F
Okumura
Shigetsugu
S
Hatakeyama
Masaki
M
Matsumoto
Takumi
T
Kamura
Keiichi I
KI
Nakayama
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D018274:Electroporation; D000939:Epitopes / Q000737:chemistry; D005799:Genes, Dominant; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D008239:Lysine / Q000737:chemistry; D009154:Mutation; D020932:Nerve Growth Factor / Q000378:metabolism; D009419:Nerve Tissue Proteins; D016501:Neurites / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D016716:PC12 Cells; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D034622:RNA Interference; D051381:Rats; D012190:Retroviridae / Q000235:genetics; D013997:Time Factors; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D000099221:Protein Kinase C zeta
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D000939:Epitopes; D008239:Lysine; D020932:Nerve Growth Factor; D009419:Nerve Tissue Proteins; D011493:Protein Kinase C; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D000099221:Protein Kinase C zeta; C528597:FEZ1 protein, human; C118711:LZTS1 protein, human; C473697:UBE4B protein, human