title: KFERQ sequence in ribonuclease A-mediated cytotoxicity.
abstract: Onconase(ONC) is an amphibian ribonuclease that is in clinical trials as a cancer chemotherapeutic agent. ONC is a homolog of ribonuclease A (RNase A). RNase A can be made toxic to cancer cells by replacing Gly(88) with an arginine residue, thereby enabling the enzyme to evade the endogenous cytosolic ribonuclease inhibitor protein (RI). Unlike ONC, RNase A contains a KFERQ sequence (residues 7-11), which signals for lysosomal degradation. Here, substitution of Arg(10) of the KFERQ sequence has no effect on either the cytotoxicity of G88R RNase A or its affinity for RI. In contrast, K7A/G88R RNase A is nearly 10-fold more cytotoxic than G88R RNase A and has more than 10-fold less affinity for RI. Up-regulation of the KFERQ-mediated lysosomal degradation pathway has no effect on the cytotoxicity of these ribonucleases. Thus, KFERQ-mediated degradation does not limit the cytotoxicity of RNase A variants. Moreover, only two amino acid substitutions (K7A and G88R) are shown to endow RNase A with cytotoxic activity that is nearly equal to that of ONC.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: Marcia C
authors.initials: MC
authors.lastname: Haigis
authors.forename: Erin L
authors.initials: EL
authors.lastname: Kurten
authors.forename: Richele L
authors.initials: RL
authors.lastname: Abel
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Raines
mesh_terms: D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D020014:K562 Cells; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D012259:Ribonuclease, Pancreatic