title: Cathepsin S, but not cathepsin L, participates in the MHC class II-associated invariant chain processing in large yellow croaker (Larimichthys crocea).
abstract: Two cysteine proteases, cathepsin S (CatS) and cathepsin L (CatL), have been identified as the key enzymes involved in the processing of invariant chain (Ii chain) in mammals. However, little is known about the roles of fish cathepsins in the Ii chain processing. In this study, large yellow croaker cathepsin S (LycCatS) and L (LycCatL) were identified and characterized. Based on the sequence comparison and phylogenetic analysis, both LycCatS and LycCatL are highly conserved to their counterparts in teleost. These two cathepsins were constitutively expressed in all tissues and immune-related cells tested, although at different levels. Both recombinant LycCatS (rLycCatS) and LycCatL (rLycCatL) possess the typical cysteine protease activity. Like other mammalian endopeptidase cathepsins, rLycCatS and rLycCatL could be autocatalytically activated to remove propeptides and release active mature peptides. On the other hand, the autocatalytic activation of rLycCatL could be inhibited by recombinant large yellow croaker Ii chain (rLyc-TR-Ii), but the autocatalytic activation of rLycCatS was not affected by rLyc-TR-Ii. Furthermore, the activated rLycCatS can efficiently process rLyc-TR-Ii in a stepwise manner in vitro, while the activated rLycCatL can not. These data indicate that cathepsin S may be the main cathepsin involved in the Ii chain processing in bony fish.
authors.affiliation: School of Marine Sciences, Ningbo University, Ningbo 315211, China; Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Qiuhua
authors.initials: Q
authors.lastname: Li
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China. Electronic address: ajingqun@tio.org.cn.
authors.forename: Jingqun
authors.initials: J
authors.lastname: Ao
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Yinnan
authors.initials: Y
authors.lastname: Mu
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China; South China Sea Bio-Resource Exploration and Utilization Collaborative Innovation Center, Xiamen 361005, China.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics* / Q000378:metabolism; D056668:Cathepsin L / Q000235:genetics* / Q000378:metabolism; D002403:Cathepsins / Q000235:genetics* / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005802:Genes, MHC Class II; D000949:Histocompatibility Antigens Class II / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010473:Perciformes / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D029941:Fish Proteins; D000949:Histocompatibility Antigens Class II; C045084:invariant chain; D002403:Cathepsins; D056668:Cathepsin L; C028217:cathepsin S
keywords: Antigen presentation; Cathepsin L; Cathepsin S; Invariant chain processing; Large yellow croaker (Larimichthys crocea)