Regulation of in vitro and in vivo immune functions by the cytosolic adaptor protein SKAP-HOM.
SKAP-HOM is a cytosolic adaptor protein representing a specific substrate for the Src family protein tyrosine kinase Fyn. Previously, several groups have provided experimental evidence that SKAP-HOM (most likely in cooperation with the cytosolic adaptor protein ADAP) is involved in regulating leukocyte adhesion. To further assess the physiological role of SKAP-HOM, we investigated the immune system of SKAP-HOM-deficient mice. Our data show that T-cell responses towards a variety of stimuli are unaffected in the absence of SKAP-HOM. Similarly, B-cell receptor (BCR)-mediated total tyrosine phosphorylation and phosphorylation of Erk, p38, and JNK, as well as immunoreceptor-mediated Ca(2+) responses, are normal in SKAP-HOM(-/-) animals. However, despite apparently normal membrane-proximal signaling events, BCR-mediated proliferation is strongly attenuated in the absence of SKAP-HOM(-/-). In addition, adhesion of activated B cells to fibronectin (a ligand for beta1 integrins) as well as to ICAM-1 (a ligand for beta2 integrins) is strongly reduced. In vivo, the loss of SKAP-HOM results in a less severe clinical course of experimental autoimmune encephalomyelitis following immunization of mice with the encephalitogenic peptide of MOG (myelin oligodendrocyte glycoprotein). This is accompanied by strongly reduced serum levels of MOG-specific antibodies and lower MOG-specific T-cell responses. In summary, our data suggest that SKAP-HOM is required for proper activation of the immune system, likely by regulating the cross-talk between immunoreceptors and integrins.
Togni
M
M
Institute of Immunology, Otto von Guericke University, Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany.
Swanson
K D
KD
Reimann
S
S
Kliche
S
S
Pearce
A C
AC
Simeoni
L
L
Reinhold
D
D
Wienands
J
J
Neel
B G
BG
Schraven
B
B
Gerber
A
A
D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002448:Cell Adhesion / Q000276:immunology; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D006413:Hematopoietic System / Q000166:cytology / Q000378:metabolism; D007136:Immunoglobulins / Q000097:blood; D016023:Integrins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008817:Mice, Mutant Strains; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein / Q000276:immunology; D063308:Myelin-Oligodendrocyte Glycoprotein; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D015398:Signal Transduction
D048868:Adaptor Proteins, Signal Transducing; D007136:Immunoglobulins; D016023:Integrins; D047908:Intracellular Signaling Peptides and Proteins; C571327:Mog protein, mouse; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D063308:Myelin-Oligodendrocyte Glycoprotein; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; C116431:src kinase associated phosphoprotein 2; D020928:Mitogen-Activated Protein Kinases