No role for pepstatin-A-sensitive acidic proteinases in reovirus infections of L or MDCK cells.
Strong evidence indicates that virions of mammalian reoviruses undergo proteolytic processing by acid-dependent cellular proteinases as an essential step in productive infection. Proteolytic processing takes the form of a series of cleavages of outer-capsid proteins final sigma3 and mu1/mu1C. Previous studies showed an effect of both NH4Cl and E-64 on these cleavages, indicating that one or more of the acid-dependent cysteine proteinases in mammalian cells (cathepsins B and L, for example) is required; however, these studies did not address whether acid-dependent aspartic proteinases in those cells (cathepsin D, for example) may also be required. To determine the role of aspartic proteinases in reovirus entry, studies with pepstatin A, a specific inhibitor of aspartic proteinases, were performed. The results showed that pepstatin A neither blocks nor slows reovirus infection of L or MDCK cells. Experiments using ribonuclease A and other proteins as cleavable substrates showed that cathepsin-D-like proteinases from these cells are inhibited within the tested range of pepstatin A concentrations both in vitro and within living cells. In other experiments, virion-bound final sigma3 protein was shown to be a poor substrate for cleavage by cathepsin D in vitro, consistent with the findings with inhibitors. In sum, the data indicate that cathepsin-D-like aspartic proteinases provide little or no activity toward proteolytic events required for infection of L or MDCK cells with reovirus virions.
Kothandaraman
S
S
College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA.
Hebert
M C
MC
Raines
R T
RT
Nibert
M L
ML
D000818:Animals; D002213:Capsid / Q000378:metabolism; D036022:Capsid Proteins; D002402:Cathepsin D / Q000037:antagonists & inhibitors / Q000502:physiology*; D002460:Cell Line; D004285:Dogs; D007668:Kidney / Q000821:virology; D007739:L Cells; D051379:Mice; D010436:Pepstatins / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012087:Reoviridae / Q000187:drug effects / Q000254:growth & development / Q000472:pathogenicity*; D012259:Ribonuclease, Pancreatic / Q000378:metabolism; D014771:Virion / Q000378:metabolism
D036022:Capsid Proteins; D010436:Pepstatins; D011480:Protease Inhibitors; D016601:RNA-Binding Proteins; C053179:sigma protein 3, Reovirus; C014195:Streptomyces pepsin inhibitor; D012259:Ribonuclease, Pancreatic; D002402:Cathepsin D; C031375:pepstatin