Human parvovirus B19 nonstructural protein NS1 enhanced the expression of cleavage of 70 kDa U1-snRNP autoantigen.
BACKGROUND
Human parvovirus B19 (B19) is known to induce apoptosis that has been associated with a variety of autoimmune disorders. Although we have previously reported that B19 non-structural protein (NS1) induces mitochondrial-dependent apoptosis in COS-7 cells, the precise mechanism of B19-NS1 in developing autoimmunity is still obscure.


METHODS
To further examine the effect of B19-NS1 in presence of autoantigens, COS-7 cells were transfected with pEGFP, pEGFP-B19-NS1 and pEGFP-NS1K334E, a mutant form of B19-NS1, and detected the expressions of autoantigens by various autoantibodies against Sm, U1 small nuclear ribonucleoprotein (U1-snRNP), SSA/Ro, SSB/La, Scl-70, Jo-1, Ku, and centromere protein (CENP) A/B by using Immunoblotting.


RESULTS
Significantly increased apoptosis was detected in COS-7 cells transfected with pEGFP-B19-NS1 compared to those transfected with pEGFP. Meanwhile, the apoptotic 70 kDa U1-snRNP protein in COS-7 cells transfected with pEGFP-B19-NS1 is cleaved by caspase-3 and converted into a specific 40 kDa product, which were recognized by anti-U1-snRNP autoantibody. In contrast, significantly decreased apoptosis and cleaved 40 kDa product were observed in COS-7 cells transfected with pEGFP-NS1K334E compared to those transfected with pEGFP-B19-NS1.


CONCLUSIONS
These findings suggested crucial association of B19-NS1 in development of autoimmunity by inducing apoptosis and specific cleavage of 70 kDa U1-snRNP.
Tzang
Bor-Show
BS
Department of Biochemistry, School of Medicine, Chung Shan Medical University, Taichung, Taiwan.
Chen
Der-Yuan
DY
Tsai
Chun-Chou
CC
Chiang
Szu-Yi
SY
Lin
Tsung-Ming
TM
Hsu
Tsai-Ching
TC
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D001324:Autoantigens / Q000378:metabolism*; D001327:Autoimmune Diseases / Q000209:etiology / Q000276:immunology / Q000473:pathology; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010322:Parvoviridae Infections / Q000209:etiology / Q000276:immunology / Q000473:pathology; D016732:Parvovirus B19, Human / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000276:immunology* / Q000378:metabolism*; D014162:Transfection; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*
D001324:Autoantigens; D017931:DNA Primers; D004279:DNA, Viral; C106202:NS1 protein, parvovirus; D011993:Recombinant Fusion Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; C490688:SNRNP70 protein, human; D017361:Viral Nonstructural Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins