Function of fusion regulatory proteins (FRPs) in immune cells and virus-infected cells.
Two molecules that regulate cell fusion have been identified and designated fusion regulatory protein-1 (FRP-1) and FRP-2. FRP-1 is a complex composed of a glycosylated heavy chain and a nonglycosylated light chain that are disulfide linked. FRP-1 heavy chain is identical to 4F2/CD98 heavy chain, whereas FRP-2 is identical to integrin alpha3 subunit. The FRP-1 heavy chain is a multifunctional molecule: that is, fusion regulator, amino acid transporter, integrin regulator, comitogenic factor, Na+-Ca2+ exchanger, oncogenic protein, and so on. Several aspects of the structure and function of the FRP-1 system are reviewed: fusion regulatory molecular mechanisms, cross-talk between the FRP-1 and integrin, the FRP-1 system as amino acid transporter, and FRP-1-mediated T-cell activation. The FRP-1 system is involved in virus-mediated cell fusion and multinucleated giant cell formation of blood monocytes. Monoclonal antibodies against human FRP-1 heavy chain induce polykaryocytes that have properties as osteoclasts. Multiple steps participate in molecular mechanisms regulating cell fusion. The FRP-1 heavy chain supports amino acid transport activity and the FRP-1 light chains have recently been cloned as amino acid transporters that require association with the heavy chain to exhibit their activity. Novel pathways for monocyte-dependent regulation of T-cell activation have recently been found that are mediated by the FRP-1 system. In conclusion, the FRP-1 molecules are essential factors for basic cellular functions.
Tsurudome
M
M
Department of Microbiology, Mie University School of Medicine, Tsu, Japan.
Ito
Y
Y
D000596:Amino Acids / Q000378:metabolism; D015703:Antigens, CD / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism / Q000502:physiology*; D005075:Biological Evolution; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism / Q000502:physiology*; D002459:Cell Fusion; D027261:Fusion Regulatory Protein-1; D006678:HIV / Q000502:physiology*; D006801:Humans; D039422:Integrin alpha3; D016023:Integrins / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism / Q000502:physiology*; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008954:Models, Biological; D009522:Newcastle disease virus / Q000502:physiology*
D000596:Amino Acids; D015703:Antigens, CD; D002352:Carrier Proteins; D027261:Fusion Regulatory Protein-1; D039422:Integrin alpha3; D016023:Integrins