NGX6a is degraded through a proteasome-dependent pathway without ubiquitination mediated by ezrin, a cytoskeleton-membrane linker.
Our previous study demonstrated that the NGX6b gene acts as a suppressor in the invasion and migration of nasopharyngeal carcinoma (NPC). Recently, we identified the novel isoform NGX6a, which is longer than NGX6b. In this study, we first found that NGX6a was degraded in NPC cells and that this degradation was mediated by ezrin, a linker between membrane proteins and the cytoskeleton. Specific siRNAs against ezrin increase the protein level of NGX6a in these cells. During degradation, NGX6a is not ubiquitinated but is degraded through a proteasome-dependent pathway. The distribution pattern of ezrin was negatively associated with NGX6a in an immunochemistry analysis of a nasopharyngeal carcinoma tissue microarray and fetus multiple organ tissues and Western blot analysis in nasopharyngeal and NPC cell lines, suggesting that ezrin and NGX6a are associated and are involved in the progression and invasion of NPC. By mapping the interacting binding sites, the seven-transmembrane domain of NGX6a was found to be the critical region for the degradation of NGX6a, and the amino terminus of ezrin is required for the induction of NGX6a degradation. The knockdown of ezrin or transfection of the NGX6a mutant CO, which has an EGF-like domain and a transmembrane 1 domain, resulted in no degradation, significantly reducing the ability of invasion and migration of NPC cells. This study provides a novel molecular mechanism for the low expression of NGX6a in NPC cells and an important molecular event in the process of invasion and metastasis of nasopharyngeal carcinoma cells.
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, the Department of Cardio-Thoracic Surgery, Second Xiangya Hospital of Central South University, 139 Renmin Middle Road, Changsha, Hunan 410012, China, and.
Li
L
Wang
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China.
Xiaoling
X
Li
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China.
Bo
B
Xiang
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China.
Ming
M
Zhou
the Third Xiang-Ya Hospital, Central South University, Changsha, Hunan 410013, China.
Xiayu
X
Li
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China.
Wei
W
Xiong
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China.
Man
M
Niu
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China.
Pingpin
P
Wei
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China.
Zeyou
Z
Wang
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China.
Heran
H
Wang
From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China.
Pan
P
Chen
the Third Xiang-Ya Hospital, Central South University, Changsha, Hunan 410013, China.
Shourong
S
Shen
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China, shuping@csu.edu.cn.
Shuping
S
Peng
the Cancer Research Institute, Central South University, Changsha, Hunan 410078, China, From the Hunan Provincial Tumor Hospital and the Affiliated Tumor Hospital of Xiangya School of Medicine, Central South University, 582 Xianjiahu Road, Changsha, Hunan 410013, China, lgy@csu.edu.cn.
Guiyuan
G
Li
D002277:Carcinoma; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000378:metabolism; D059748:Proteolysis; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D054875:Ubiquitination; D000099149:Ezrin
D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D046988:Proteasome Endopeptidase Complex; D020033:Protein Isoforms; D025521:Tumor Suppressor Proteins; D000099149:Ezrin; C477325:TMEM8B protein, human
Biodegradation; Cancer; Degradation; Ezrin; Metastasis; NGX6a; Nasopharyngeal Carcinoma; Ubiquitylation (Ubiquitination)