2',5'-Oligoadenylate size is critical to protect RNase L against proteolytic cleavage in chronic fatigue syndrome.
A dysregulation in the 2',5'-oligoadenylate (2-5A)-dependent RNase L antiviral pathway has been detected in peripheral blood mononuclear cells (PBMC) of chronic fatigue syndrome (CFS) patients, which is characterized by upregulated 2-5A synthetase and RNase L activities, as well as by the presence of a low molecular weight (LMW) 2-5A-binding protein of 37-kDa related to RNase L. This truncated protein has been shown to originate from proteolytic cleavage of the native 83-kDa RNase L by m-calpain and human leukocyte elastase (HLE). We investigated the possible role of 2-5A oligomers in the proteolytic action toward the endonuclease and show that incubation of CFS PBMC extracts with 2-5A trimer and tetramer, but not with the dimer, results in a significant protection of the native 83-kDa RNase L against cleavage by endogenous and purified proteases. Similar results are obtained with a purified recombinant RNase L. An analysis of the size of 2-5A oligomers produced by the catalytic activity of the 2-5A synthetase present in PBMC extracts further shows that samples containing the 37-kDa RNase L preferentially produce 2-5A dimers instead of higher oligomers. Taken together, our results indicate that homodimerization of RNase L by 2-5A oligomers higher than the dimer prevents its cleavage by proteolytic enzymes. The presence of the truncated 37-kDa RNase L in PBMC extracts is therefore likely to result, not only from the abnormal activation of inflammatory proteases, but also from a dysregulation in 2-5A synthetase induction or activation towards the preferential production of 2-5A dimers.
Frémont
Marc
M
RED Laboratories, Pontbeek 61, B-1731 Zellik, Belgium.
El Bakkouri
Karim
K
Vaeyens
Freya
F
Herst
C Vincent
CV
De Meirleir
Kenny
K
Englebienne
Patrick
P
D000227:Adenine Nucleotides / Q000378:metabolism*; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004722:Endoribonucleases / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D015673:Fatigue Syndrome, Chronic / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D007963:Leukocytes, Mononuclear / Q000201:enzymology*; D009843:Oligoribonucleotides / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
D000227:Adenine Nucleotides; D009843:Oligoribonucleotides; D010455:Peptides; D011994:Recombinant Proteins; C023505:2',5'-oligoadenylate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease