The protein made from a common allele of KIR3DL1 (3DL1*004) is poorly expressed at cell surfaces due to substitution at positions 86 in Ig domain 0 and 182 in Ig domain 1.
KIR3DL1 is an inhibitory HLA-B receptor of human NK and T cells that exhibits genetic and phenotypic polymorphism. KIR3DL1*004, a common allotype, cannot be detected on the surface of PBLs using the KIR3DL1-specific Ab DX9. The nature of this phenotype was investigated through comparison of 3DL1*004 with 3DL1*002, an allele giving high DX9 binding to cell surfaces. Analysis of Jurkat T cell transfectants with 3DL1*004 cDNA showed that 3DL1*004 is poorly expressed at the cell surface, but detectable intracellularly. Analysis of recombinant mutants made between 3DL1*004 and 3DL1*002 showed that polymorphism in Ig domains 0 and 1 (D0 and D1) causes the intracellular retention of 3DL1*004. Reciprocal point mutations were introduced into 3DL1*004 and 3DL1*002 at positions 44 and 86 of the D0 domain, where 3DL1*004 has unique residues, and at position 182 of the D1 domain, where 3DL1*004 resembles 3DL1*005, an allotype giving low DX9-binding phenotype. Leucine 86 in 3DL1*004 is the principal cause of its intracellular retention, with a secondary and additive contribution from serine 182. By contrast, glycine 44, which is naturally present in 3DL1*004, slightly increased cell surface expression when introduced into 3DL1*002. In 3DL1*004, the presence of leucine at position 86 corrupts the WSXPS motif implicated in proper folding of the KIR D0 Ig-like domain. This study demonstrates how a difference between KIR3DL1 allotypes in the D0 domain profoundly affects cell surface expression and function.
Pando
Marcelo J
MJ
Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305-5126, USA.
Gardiner
Clair M
CM
Gleimer
Michael
M
McQueen
Karina L
KL
Parham
Peter
P
D000483:Alleles; D019943:Amino Acid Substitution / Q000235:genetics* / Q000276:immunology*; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002999:Clone Cells; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D005110:Extracellular Space / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D016130:Immunophenotyping; D019169:Jurkat Cells; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism*; D007930:Leucine / Q000737:chemistry / Q000235:genetics; D011110:Polymorphism, Genetic / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D054340:Receptors, KIR; D054341:Receptors, KIR3DL1; D012694:Serine / Q000737:chemistry / Q000235:genetics; D014162:Transfection
D007136:Immunoglobulins; C515083:KIR3DL1 protein, human; D011971:Receptors, Immunologic; D054340:Receptors, KIR; D054341:Receptors, KIR3DL1; D012694:Serine; D007930:Leucine