2′,5′-Oligoadenylate size is critical to protect RNase L against proteolytic cleavage in chronic fatigue syndrome

• Published in: Experimental and molecular pathology 2005-06, Vol.78 (3), p.239-246
• Main Authors: Frémont, Marc, El Bakkouri, Karim, Vaeyens, Freya, Herst, C. Vincent, De Meirleir, Kenny, Englebienne, Patrick
• Format: Article
• Language: English
• Subjects: 2′,5′-oligoadenylate synthetase; 2′,5′-oligoadenylates; Adenine Nucleotides - metabolism; Biological and medical sciences; Chronic fatigue syndrome; Dimerization; Electrophoresis, Polyacrylamide Gel; Endoribonucleases - metabolism; Enzyme Activation - physiology; Fatigue Syndrome, Chronic - metabolism; Human leukocyte elastase; Humans; Immunoblotting; Investigative techniques, diagnostic techniques (general aspects); Leukocytes, Mononuclear - enzymology; M-calpain; Medical sciences; Oligoribonucleotides - metabolism; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Peptides - metabolism; Protein cleavage; Recombinant Proteins - metabolism; Ribonuclease L; Substrate Specificity
• ISSN: 0014-4800; 1096-0945
• DOI: 10.1016/j.yexmp.2005.01.003

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.