PHOENIX RISING

 RNase L and Chronic Fatigue Syndrome (ME/CFS) : 2-5OAS and RNase L by Cort Johnson

WARNING!  This contains rather technical background information on the 2-5A/RNase L system. Only RNase L junkies need continue further. 

Player, M. R. and P. F. Torrence. 1998. The 2-5A system: modulation of viral and cellular processes through acceleration of RNA degration. Pharmacological Ther 78: 55-113. 

    (Thank God for review articles such as this one.  Too bad they come along so infrequently.)  We learned in CFS ABA that Type I IFN's were mainly involved in 2-5OAS activation. In this article we learn that Type II IFN's (IFN-y) are also able to induce RNase L but do so less efficiently.  The possibility Englebienne mentioned that the aberrant 2-5A induction seen in CFS could be the result of dysfunctional IFN signaling is made clear when the authors note that many types of IFN a/b/y exist and that each may induce a different 2-5OAS isoform (p40, 44, 69, 100). 

The IFN system is not dependent on RNase L for antiviral activity.  IFN induced antiviral activity has been demonstrated during periods when RNase L is inactive.  RNase L has exhibited antiviral activity again viruses belonging to the picornaviruses (enteroviruses (polio)), rhinoviruses, cardioviruses (EMCV), reoviruses, poxviruses (vaccinia).  2-5A has a short half-life in the cell.  It is rapidly degraded by phosphodiesterases in the cell. 

IFN's, interestingly enough, are not the only inducers of 2-5OAS.  Glucocorticoids, several growth factors, protein kinase C and the anti-estrogen Tamoxifen appear to be able to either enhance or induce 2-5OAS.  Some substances can decrease 2-5OAS activity.  These include arachidonic acid, gangliosides and glucose. 

We also learn that while 2-5OAS induction commonly occurs in response to viral attack, not all viruses induce 2-5OAS activity and some viruses (mump virus) appear to suppress 2-5OAS. 

Both Type I IFN's and 2-5OAS appear to be able to block cell growth.  Levels of both rise 10fold in the late S phase of cellular development.  Cellular growth inhibition has been correlated with increased levels of 2-5OAS in several studies. Increased 2-5OAS levels are positively correlated, as well, with cell differentiation and maturation.  (This is why cancer researchers are so interested in 2-5OAS.  Harnessing it to control the differentiation and maturation of cancer cells could be very beneficial.) Cell growth inhibition appears, at least in one cell line, no to require IFN activation. RNase L appears, as we learned in CFS ABA, to be involved in muscle cell differentiation.  Altered 2-5OAS activity in virally infected muscle cells undergoing differentiation suggested that viral infection may disrupt 2-5OAS functioning.  (And that viral infection can disrupt muscle cell differentiation.)i 

An intriguing but unproven interaction with energy production involves RNase L's ability to 'adenylate' (and inactivate) NAD+, an important element in cellular metabolism.  Researchers have yet to find an evidence, however that 2-5OAS plays a role in cellular metabolism. 

The Isoforms of 2-5OAS - The apparent dominance of the p100 isoform of the 2-5OAS enzyme appears to lie at the heart of RNase L dysfunction.  The different isoforms are coded for by different types of mRNA.  The p40 and p46 isoforms are coded by 1.6 and 1.8 Kb mRNA's.  The p40. p46 and p69 isoforms appear to exist as tetramers and dimers respectively.  The p100 isoforms appears to be a monomer.  The 40 kDa isoform is espressed as a glutathione S-transferase in E. coli (what does this mean? 2-5OAS is similar to glutathione transferase?))

Both the p69 and the p100 isoforms are found in the cytoplasm but p69 is found in close association with the nuclear membrane while  p100 is found only in microsomes.  (The mRNA that activates p100 must then originate from pathogens in the cytoplasm???).  The binding site for dsRNA on 2-5OAS is not known.  It appears, however, that the binding sites may differ between the isoenzymes.  (More evidence of differentiation more heterogeneity in these isoforms. This provides more indirect evidence that one anomalous type of RNA specifically targets the p100 2-5OAS enzyme in CFS patients.)

2-5OAS activity is greatest when prompted by dsRNA that is 65-80 bp's long.  Both p69 and p100 can be activated by similar types of (manufactured) dsRNA.  The authors state, interestingly enough, that the misaligned dsRNA Ampligen potently activates both the p69 and p100 isoforms.  (Given Ampligens ability to reregulate 2-5OAS activity in CFS patients it seems odd, to say the least, that it would activate the very isoform that is upregulated. 

RNase L Activities in the Body -  Most interesting, given the subsequent reports of unusual RBC morphology are studies indicatiing that the 2-5OAS RNase L system may be involved in regulation RBC formation.  Also intriguing, given the possibility of hypercoagulation in CFS patients, are reports that RNase L may also play a role in blood clotting..  A mitogen (growth inducing agent) called platelet derived growth factor (PGDF) that is released during the clotting process stimulates the 2-5OAS and IFN b genes.  

It appears that the heat shock proteins (HSP's) released during increased temperature and/or toxin exposure are able to induce 2-5OAS activity as well. (Ethanol is able, in fact, to induce an antiviral state in cells!)  Researchers theorize that 2-5OAS and RNase L may function as regulatory agents of PGDF and HSP activity.  They speculate that high PGDF or HSP activity may induce RNase L to destroy PGDF or HSP mRNA in order to lower stress levels.

Autoimmunity and RNase L – Only the 2-5A dimer was found in the blood of autoimmune rats (!). Upon administration of poly (1) poly (C) (?)  (in the absence of IFN production) only 2-5A dimers were produced in the cells of autoimmune Type I diabetes patients.  Longer 2-5a products required IFN administration.  (This indicates that 2-5OAS is not dependent upon IFN for activation. Could 2-5A dimer production be a natural consequence of a blocked IFN signal because of STAT I degradation?)