Differentiation of human T cells alters their repertoire of G protein alpha-subunits.
Because T cell differentiation leads to an expanded repertoire of chemokine receptors, a subgroup of G protein-coupled receptors, we hypothesized that the repertoire of G proteins might be altered in parallel. We analyzed the abundance of mRNA and/or protein of six G protein α-subunits in human CD4(+) and CD8(+) T cell subsets from blood. Although most G protein α-subunits were similarly expressed in all subsets, the abundance of Gα(o), a protein not previously described in hematopoietic cells, was much higher in memory versus naive cells. Consistent with these data, activation of naive CD4(+) T cells in vitro significantly increased the abundance of Gα(o) in cells stimulated under nonpolarizing or T(H)17 (but not T(H)1 or T(H)2)-polarizing conditions. In functional studies, the use of a chimeric G protein α-subunit, Gα(qo5), demonstrated that chemokine receptors could couple to Gα(o)-containing G proteins. We also found that Gα(i1), another α-subunit not described previously in leukocytes, was expressed in naive T cells but virtually absent from memory subsets. Corresponding to their patterns of expression, siRNA-mediated knockdown of Gα(o) in memory (but not naive) and Gα(i1) in naive (but not memory) CD4(+) T cells inhibited chemokine-dependent migration. Moreover, although even in Gα(o)- and Gα(i1)-expressing cells mRNAs of these α-subunits were much less abundant than Gα(i2) or Gα(i3), knockdown of any of these subunits impaired chemokine receptor-mediated migration similarly. Together, our data reveal a change in the repertoire of Gα(i/o) subunits during T cell differentiation and suggest functional equivalence among Gα(i/o) subunits irrespective of their relative abundance.
Foley
John F
JF
Inflammation Biology Section, Laboratory of Molecular Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA.
Singh
Satya P
SP
Cantu
Michelle
M
Chen
Lingye
L
Zhang
Hongwei H
HH
Farber
Joshua M
JM
D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000378:metabolism; D002633:Chemotaxis / Q000235:genetics; D005260:Female; D005312:Fetal Blood / Q000166:cytology; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D057809:HEK293 Cells; D006801:Humans; D007231:Infant, Newborn; D019169:Jurkat Cells; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D011247:Pregnancy; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054399:Receptors, CCR6 / Q000235:genetics / Q000378:metabolism; D000075744:Receptors, CXCR6; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C106311:CCR6 protein, human; C106330:CXCR6 protein, human; D054377:Chemokine CXCL12; D044385:GTP-Binding Protein alpha Subunits; D012333:RNA, Messenger; D054399:Receptors, CCR6; D000075744:Receptors, CXCR6; D019707:Receptors, Chemokine; D011991:Receptors, Virus; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go