SHPS-1 induces aggregation of Ba/F3 pro-B cells via an interaction with CD47.
SHPS-1 (SH2-domain bearing protein tyrosine phosphatase (SHP) substrate-1), a member of the inhibitory-receptor superfamily that is abundantly expressed in macrophages and neural tissue, appears to regulate intracellular signaling events downstream of receptor protein-tyrosine kinases and integrin-extracellular matrix molecule interactions. To investigate the function of SHPS-1 in a hematopoietic cell line, SHPS-1 was expressed in Ba/F3 cells, an IL-3-dependent pro-B-cell line that lacks endogenous SHPS-1 protein. Interestingly, expression of either SHPS-1, or a mutant lacking the intracellular domain of SHPS-1 (DeltaCT SHPS-1), resulted in the rapid formation of macroscopic Ba/F3 cell aggregates. As the integrin-associated protein/CD47 was shown to be a SHPS-1 ligand in neural cells, we investigated whether CD47 played a role in the aggregation of SHPS-1-expressing Ba/F3 cells. In support of this idea, aggregate formation was inhibited by an anti-CD47 Ab. Furthermore, erythrocytes from control, but not from CD47-deficient mice, were able to form rosettes on SHPS-1-expressing Ba/F3 cells. Because erythrocytes do not express integrins, this result suggested that SHPS-1-CD47 interactions can take place in the absence of a CD47-integrin association. We also present evidence that the amino-terminal Ig domain of SHPS-1 mediates the interaction with CD47. Although SHPS-1-CD47 binding likely triggers bidirectional intracellular signaling processes, these results demonstrate that this interaction can also mediate cell-cell adhesion.
Babic
I
I
Centre for Molecular Medicine and Therapeutics, British Columbia Research Institute for Children's and Women's Health, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
Schallhorn
A
A
Lindberg
F P
FP
Jirik
F R
FR
D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D000943:Antigens, Differentiation; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D051928:CD47 Antigen; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D002449:Cell Aggregation / Q000235:genetics / Q000276:immunology; D002450:Cell Communication / Q000235:genetics / Q000276:immunology*; D002460:Cell Line; D005110:Extracellular Space / Q000276:immunology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D010446:Peptide Fragments / Q000502:physiology; D017434:Protein Structure, Tertiary; D051381:Rats; D011971:Receptors, Immunologic; D012397:Rosette Formation; D013234:Stem Cells / Q000276:immunology*
D019138:Antibodies, Blocking; D015703:Antigens, CD; D000943:Antigens, Differentiation; D051928:CD47 Antigen; D002352:Carrier Proteins; C497895:Cd47 protein, mouse; D008562:Membrane Glycoproteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D010446:Peptide Fragments; C501922:Sirpa protein, mouse; D011971:Receptors, Immunologic; C501924:Sirpa protein, rat