Phosphoserine acidic cluster motifs bind distinct basic regions on the μ subunits of clathrin adaptor protein complexes

J Biol Chem. 2018 Oct 5;293(40):15678-15690. doi: 10.1074/jbc.RA118.003080. Epub 2018 Aug 22.

Abstract

Protein trafficking in the endosomal system involves the recognition of specific signals within the cytoplasmic domains (CDs) of transmembrane proteins by clathrin adaptors. One such signal is the phosphoserine acidic cluster (PSAC), the prototype of which is in the endoprotease furin. How PSACs are recognized by clathrin adaptors has been controversial. We reported previously that HIV-1 Vpu, which modulates cellular immunoreceptors, contains a PSAC that binds to the μ subunits of clathrin adaptor protein (AP) complexes. Here, we show that the CD of furin binds the μ subunits of AP-1 and AP-2 in a phosphorylation-dependent manner. Moreover, we identify a potential PSAC in a cytoplasmic loop of the cellular transmembrane Serinc3, an inhibitor of the infectivity of retroviruses. The two serines within the PSAC of Serinc3 are phosphorylated by casein kinase II and mediate interaction with the μ subunits in vitro The sites of these serines vary among mammals in a manner suggesting host-pathogen conflict, yet the Serinc3 PSAC seems dispensable for anti-HIV activity and for counteraction by HIV-1 Nef. The CDs of Vpu and furin and the PSAC-containing loop of Serinc3 each bind the μ subunit of AP-2 (μ2) with similar affinities, but they appear to utilize different basic regions on μ2. The Serinc3 loop requires a region previously reported to bind the acidic plasma membrane lipid phosphatidylinositol 4,5-bisphosphate. These data suggest that the PSACs within different proteins recognize different basic regions on the μ surface, providing the potential to inhibit the activity of viral proteins without necessarily affecting cellular protein trafficking.

Keywords: HIV-1 Vpu; Serinc3; acidic cluster; adaptor protein; clathrin; furin; host-pathogen interaction; human immunodeficiency virus (HIV); kinetics; medium subunit; membrane trafficking; phosphorylation; phosphoserine; protein chemistry; protein complex.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Protein Complex 1 / chemistry*
  • Adaptor Protein Complex 1 / genetics
  • Adaptor Protein Complex 1 / metabolism
  • Adaptor Protein Complex 2 / chemistry*
  • Adaptor Protein Complex 2 / genetics
  • Adaptor Protein Complex 2 / metabolism
  • Amino Acid Motifs
  • Animals
  • Binding Sites
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Furin / chemistry*
  • Furin / genetics
  • Furin / metabolism
  • Gene Expression
  • HIV-1 / genetics*
  • HIV-1 / metabolism
  • Human Immunodeficiency Virus Proteins / chemistry
  • Human Immunodeficiency Virus Proteins / genetics
  • Human Immunodeficiency Virus Proteins / metabolism
  • Humans
  • Jurkat Cells / metabolism
  • Jurkat Cells / virology
  • Kinetics
  • Mammals
  • Membrane Glycoproteins
  • Models, Molecular
  • Neoplasm Proteins / chemistry*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Phosphatidylinositol 4,5-Diphosphate / chemistry
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Phosphoserine / chemistry*
  • Phosphoserine / metabolism
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Protein Subunits / chemistry
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Receptors, Cell Surface / chemistry*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Viral Regulatory and Accessory Proteins / chemistry
  • Viral Regulatory and Accessory Proteins / genetics
  • Viral Regulatory and Accessory Proteins / metabolism
  • Virion / genetics
  • Virion / metabolism
  • nef Gene Products, Human Immunodeficiency Virus / chemistry
  • nef Gene Products, Human Immunodeficiency Virus / genetics
  • nef Gene Products, Human Immunodeficiency Virus / metabolism

Substances

  • Adaptor Protein Complex 1
  • Adaptor Protein Complex 2
  • Human Immunodeficiency Virus Proteins
  • Membrane Glycoproteins
  • Neoplasm Proteins
  • Phosphatidylinositol 4,5-Diphosphate
  • Protein Subunits
  • Receptors, Cell Surface
  • Recombinant Proteins
  • SERINC3 protein, human
  • Viral Regulatory and Accessory Proteins
  • nef Gene Products, Human Immunodeficiency Virus
  • nef protein, Human immunodeficiency virus 1
  • vpu protein, Human immunodeficiency virus 1
  • Phosphoserine
  • FURIN protein, human
  • Furin

Associated data

  • PDB/4EN2
  • PDB/1BW8
  • PDB/2XA7