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

Exp Mol Pathol. 2005 Jun;78(3):239-46. doi: 10.1016/j.yexmp.2005.01.003. Epub 2005 Mar 2.

Abstract

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.

Publication types

  • Comparative Study

MeSH terms

  • Adenine Nucleotides / metabolism*
  • Dimerization
  • Electrophoresis, Polyacrylamide Gel
  • Endoribonucleases / metabolism*
  • Enzyme Activation / physiology
  • Fatigue Syndrome, Chronic / metabolism*
  • Humans
  • Immunoblotting
  • Leukocytes, Mononuclear / enzymology*
  • Oligoribonucleotides / metabolism*
  • Peptides / metabolism
  • Recombinant Proteins / metabolism
  • Substrate Specificity

Substances

  • Adenine Nucleotides
  • Oligoribonucleotides
  • Peptides
  • Recombinant Proteins
  • 2',5'-oligoadenylate
  • Endoribonucleases
  • 2-5A-dependent ribonuclease