TC-PTP–deficient bone marrow stromal cells fail to support normal B lymphopoiesis due to abnormal secretion of interferon-γ

Abstract

The T-cell protein tyrosine phosphatase (TC-PTP) is a negative regulator of the Jak/Stat cytokine signaling pathway. Our study shows that the absence of TC-PTP leads to an early bone marrow B-cell deficiency characterized by hindered transition from the pre-B cell to immature B-cell stage. This phenotype is intrinsic to the B cells but most importantly due to bone marrow stroma abnormalities. We found that bone marrow stromal cells from TC-PTP ؊ IntroductionThe T-cell protein tyrosine phosphatase (TC-PTP) is an intracellular enzyme encoded by Ptpn2. It is ubiquitously expressed, with highest levels in hematopoietic tissues (for a review, see Bourdeau et al 1 ). TC-PTP Ϫ/Ϫ mice appear physically normal until 10 to 14 days of age, at which time they progressively develop tissue mononuclear cell infiltrates. 2 Elevated levels of IFN-␥ can be measured at 19 days of age, 3 and the animals die between 21 and 35 days of age. TC-PTP Ϫ/Ϫ mice display defective hematopoiesis and immune function, characterized by anemia and splenomegaly secondary to sequestration of erythrocytes and accumulation of myeloid cells. 2 TC-PTP was also shown to interact with TRAF2 downstream of the TNF proinflammatory cytokine. This interaction inactivated Src and suppressed MAPK signaling. 4 TC-PTP has been identified as a critical regulator of colony-stimulating factor 1 (CSF-1) signaling and mononuclear phagocyte development. On CSF-1 stimulation, a deficiency in TC-PTP leads to enhanced tyrosine phosphorylation of the Grb2/Gab2/Shp2 complex by the CSF-1 receptor and increased activation of Erk. 5 These results identified TC-PTP as a key modulator of inflammatory signals as well as macrophage and lymphocyte functions.TC-PTP has been shown to control cytokine signaling events by its negative action on the Janus kinase (Jak) and signal transducer and activator of transcription (Stat) pathways (reviewed by Bourdeau et al 1 ). This cascade is crucial for hematopoietic development and cellular response to growth factors. 6 Using an in vitro approach, TC-PTP substrate-trapping mutant D/A was shown to interact with Jak1 and Jak3. 7 Stat1, Stat3, and Stat5a/5b were also identified as substrates for TC-PTP. [8][9][10] It is clear that TC-PTP is a key director of several cytokine-signaling pathways, and thus may be involved in the development of multiple hematopoietic lineages.Here, we report that bone marrow stromal cells from TC-PTP Ϫ/Ϫ mice secrete abnormally high levels of IFN-␥, resulting in constitutive phosphorylation of Stat1 in pre-B cells and altered B-cell development in the bone marrow. Our findings are novel and reflect the therapeutic potential of TC-PTP as a modulator of bone marrow stroma microenvironment that could be exploited in leukemia and other immune disorders. Materials and methods MiceGeneration of TC-PTP mutant mice was described previously. 2 Experiments were performed with mice on a mixed Balb/c-129SJ background and with mice backcrossed for 8 generation on Balb/c. All procedures were approved by the McGill University Rese...

T cell protein tyrosine phosphatase deficiency results in spontaneous synovitis and subchondral bone resorption in mice

“…Antibodies directly conjugated with fluorescein isothiocyanate, phycoerythrin (PE), PE-Cy5, PE-Cy7, allophycocyanin (APC), APC-Cy7, or biotin were purchased from BD Biosciences or BioLegend. Cell surface staining and flow cytometry analysis were performed as previously described (3).…”

“…Mice deficient in TC-PTP die within 5 weeks after birth (2) and have defective hematopoiesis (3,4), anemia, and severe systemic progressive inflammation characterized by the infiltration of mononuclear cells in several tissues and high levels of various proinflammatory cytokines, including tumor necrosis factor ␣ (TNF␣) (5). TNF␣ plays a central role in the pathogenesis of rheumatoid arthritis (RA), as indicated in experimental models in which mice overexpressing transgenic TNF␣ develop spontaneous arthritis (6,7).…”

Protein Tyrosine Phosphatases and Type 1 Diabetes: Genetic and Functional Implications of PTPN2 and PTPN22

“…These B and T cell phenotypes result from both cell intrinsic and extrinsic factors, as evidenced by decreased B cell colony forming ability in Ptpn2 -/-bone marrow compared to Ptpn2 +/+ bone marrow when grown on wild type stromal cells, Vol. -/-stromal cells [68]. Extrinsically, cells in Ptpn2 -/-mice are exposed to increased levels of inflammatory cytokines, while intrinsically, Ptpn2 deficiency exacerbates signaling in response to growth factors, cytokines, and antigen receptor stimulation, since PTPN2 negatively regulates these pathways, as described above.…”

“…Histologically, Ptpn2 -/-mice are characterized by decreased bone marrow cellularity over time, with reduced numbers of progenitor B cells, pre B cells, immature IgM + B cells, and mature IgD + recirculating B cells, which is reflected in decreased peripheral B cell subsets [66,68]. The thymus also has decreased cellularity over time due to a reduction in CD4 + CD8…”

PTPN2 is Associated with Crohn’s Disease and Its Expression Is Regulated by NKX2-3

“…PTPN2 is involved in T-cell proliferation [21] and B cell development [22]. During development, NKX2-3 is expressed in midgut and hindgut mesoderm and spleen, as well as in pharyngeal endoderm [23,24].…”