A structural model of 20S immunoproteasomes: effect of LMP2 codon 60 polymorphism on expression, activity, intracellular localisation and insight into the regulatory mechanisms.
The immunoproteasome subunit low molecular weight protein 2 (LMP2) codon 60 polymorphism has been associated with autoimmune diseases. It has also been demonstrated to influence susceptibility to TNF-alpha-induced apoptosis in blood cells and proteasome activity in aged human brain. In the present study, an in silico model of immunoproteasome was used to examine the effect of the R60H polymorphism in the LMP2 subunit. The investigation of immunoproteasome expression, activity and intracellular localisation in an in vitro cellular model, namely lymphoblastoid cell lines, showed no major variations in functionality and amount, while a significant difference in antibody affinity was apparent. These data were integrated with previous results obtained in different tissues and combined with a structural model of the LMP2 polymorphism. Accordingly, we identified three prospective mechanisms that could explain the biological data for the polymorphism, such as modulation of the binding affinity of a putative non-catalytic modifier site on the external surface of the immunoproteasome core, or the modification of any channel between alpha and beta rings.
Mishto
Michele
M
Department of Experimental Pathology, University of Bologna, via S. Giacomo 14, I-40126 Bologna, Italy. michele.mishto@unibo.it
Santoro
Aurelia
A
Bellavista
Elena
E
Sessions
Richard
R
Textoris-Taube
Kathrin
K
Dal Piaz
Fabrizio
F
Carrard
Geraldine
G
Forti
Katia
K
Salvioli
Stefano
S
Friguet
Bertrand
B
Kloetzel
Peter M
PM
Rivett
A Jennifer
AJ
Franceschi
Claudio
C
D000911:Antibodies, Monoclonal; D002467:Cell Nucleus / Q000378:metabolism; D003062:Codon; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004789:Enzyme Activation; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism; D008958:Models, Molecular; D011110:Polymorphism, Genetic; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D013379:Substrate Specificity
D000911:Antibodies, Monoclonal; D003062:Codon; D021122:Protein Subunits; C071313:LMP-2 protein; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex