Prevalence of pyruvate kinase deficiency in a northern European population in the north of England

Earlier this year, we provided a definitive report indicating that there exist at least 3 murine survivin mRNA variants, each encoding a distinct protein.1 We demonstrated, with appropriate controls, that both survivin140 and survivin121 are able to inhibit caspase-3 activity, while survivin40 does not. In contrast to the claims of Altieri’s group in their letter, several reports support our finding that survivin interferes with caspase-3 activity. These include the following: Reed’s group reported that “survivin was able to substantially reduce caspase activity, as measured by cleavage of a tetrapeptide substrate, AspGluValAspaminofluorocoumarin. Similar results were obtained in intact cells when Survivin was overexpressed.”2(p5315) Altieri’s group noted in their Nature paper that “like other IAP proteins, survivin inhibits the terminal effectors caspase-3 and caspase-7.”3(p583) Kobayashi et al demonstrated that overexpression of murine survivin in Rat1 cells inhibited caspase-induced cell death and also that a purified GST fusion protein encoding murine survivin could bind directly to caspase-3.4 This group further transfected Jurkat cells with epitopetagged survivin and showed by immunoprecipitation with anti– caspase-3 antibodies that survivin “can bind efficiently to processed caspase 3.”4(p1460) In their Nature Cell Biology paper, Altieri’s group once again noted that survivin regulates apoptosis via caspase-3: “Expression of survivin (C84A) or survivin antisense cDNA also resulted in increased activity of the apoptosis effector caspase-3, as judged by hydrolysis of the fluorogenic caspase-3 substrate.”5(p461) Altieri’s group also performed studies on cultured endothelial cells and reported that “[r]ecombinant expression of green fluorescent protein survivin in endothelial cells reduced caspase-3 activity and counteracted apoptosis induced by tumor necrosis factor.”6(p393) And finally, a recent report confirms that the down-regulation of survivin mRNA levels by an antisense approach results in increased caspase-3 activity.7 We note that many of the data indicating that survivin interferes with caspase-3 activity predate our own and, in several cases, have actually been provided by Altieri’s group. We are not in a position to assess fully the experiments described by Altieri’s group and would point out only that they are not identical to our own, in contrast to what that group claims. In addition, we would add that we have observed that the activity of recombinant survivin is highly dependent on the method chosen for its synthesis and purification. Based on our experiments and the current published data, we believe that specific forms of survivin do inhibit caspase-3 activity. Nevertheless, we agree that the means by which survivin participates in the apoptosis balance requires further investigation, and we hypothesize that the alternatively spliced isoforms of survivin may modulate apoptosis differentially.