Autoproteolysis of the SEA module of rMuc3 C-terminal domain modulates its functional composition.
rMuc3 is a typical transmembrane mucin and contains a 174 amino acid domain called an SEA module in its C-terminal domain which is cleaved in eukaryotic cells. However, the mechanism by which the rMuc3 SEA module is proteolyzed and its biological significance has to be elucidated. In this study, we showed that the rMuc3 C-terminal domain was cleaved at LSKGSIVV motif within SEA module in prokaryotic cells, the time-dependence of the cleavage was found in the purified rMuc3 C-terminal domain carrying a mutated LSKASIVV motif expressed in bacteria. Thus, the cleavage of rMuc3 SEA module depended on autoproteolysis. The autoproteolysis of the SEA module of rMuc3 C-terminal domain played a critical role in the migration and invasion of the LoVo human colon cancer cells with rMuc3 C-terminal domain in vitro. The rMuc3 C-terminal domain induced a significant activation of HER/ErbB2 phosphorylated form (py1248) in LoVo cells. Inhibition of the phosphorylation by gefitinib (ZD1839) did attenuate migration and invasion of LoVo cells with rMuc3 C-terminal domain. Thus, rMuc3 C-terminal domain undergoes autoproteolysis at its SEA module, which maintains its availability for the potentiation of the signaling process that is modulated by HER/ErbB2 phosphorylation to promote the migration and invasion of LoVo cells.
Peng
Zhihong
Z
Institute of Gastroenterology of PLA, Southwest Hospital, Third Military Medical University, Chongqing, PR China.
He
Yonghong
Y
Yang
Yongtao
Y
Zhu
Rong
R
Bai
Jianying
J
Li
Yicheng
Y
Yu
Hao
H
Zhang
Xin
X
Chen
Lei
L
Chen
Wensheng
W
Fang
Dianchun
D
Wang
Rongquan
R
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002465:Cell Movement; D002522:Chlorocebus aethiops; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D006868:Hydrolysis; D055263:Mucin-3 / Q000737:chemistry*; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment; D014162:Transfection
D055263:Mucin-3; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; C524651:Muc3 protein, rat; C508053:ERBB2 protein, human