Low pH-triggered beta-propeller switch of the low-density lipoprotein receptor assists rhinovirus infection

J Virol. 2009 Nov;83(21):10922-30. doi: 10.1128/JVI.01312-09. Epub 2009 Aug 12.

Abstract

Minor group human rhinoviruses (HRVs) bind three members of the low-density lipoprotein receptor (LDLR) family: LDLR proper, very-LDLR (VLDLR) and LDLR-related protein (LRP). Whereas ICAM-1, the receptor of major group HRVs actively contributes to viral uncoating, LDLRs are rather considered passive vehicles for cargo delivery to the low-pH environment of endosomes. Since the Tyr-Trp-Thr-Asp beta-propeller domain of LDLR has been shown to be involved in the dissociation of bound LDL via intramolecular competition at low pH, we studied whether it also plays a role in HRV infection. Human cell lines deficient in LDLR family proteins are not available. Therefore, we used CHO-ldla7 cells that lack endogenous LDLR. These were stably transfected to express either wild-type (wt) human LDLR or a mutant with a deletion of the beta-propeller. When HRV2 was attached to the propeller-negative LDLR, a lower pH was required for conversion to subviral particles than when attached to wt LDLR. This indicates that high-avidity receptor binding maintains the virus in its native conformation. HRV2 internalization directed the mutant LDLR but not wt LDLR to lysosomes, resulting in reduced plasma membrane expression of propeller-negative LDLR. Infection assays using a CHO-adapted HRV2 variant showed a delay in intracellular viral conversion and de novo viral synthesis in cells expressing the truncated LDLR. Our data indicate that the beta-propeller attenuates the virus-stabilizing effect of LDLR binding and thereby facilitates RNA release from endosomes, resulting in the enhancement of infection. This is a nice example of a virus exploiting high-avidity multimodule receptor binding with an intrinsic release mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • HeLa Cells
  • Humans
  • Hydrogen-Ion Concentration
  • Lipoproteins, LDL / metabolism
  • Lysosomes / metabolism
  • Mutation
  • Picornaviridae Infections / metabolism*
  • Protein Structure, Secondary*
  • RNA, Viral / genetics
  • RNA, Viral / metabolism
  • Receptors, LDL / chemistry*
  • Receptors, LDL / genetics
  • Receptors, LDL / metabolism*
  • Rhinovirus / physiology*
  • Virus Attachment
  • Virus Internalization*

Substances

  • Lipoproteins, LDL
  • RNA, Viral
  • Receptors, LDL