INTRODUCTION: Autoinflammatory diseases are characterized by dysregulation of innate immune system leading to spontaneous sterile inflammation. One of the well-established animal models of this group of disorders is the mouse strain Pstpip2cmo . In this strain, the loss of adaptor protein PSTPIP2 leads to the autoinflammatory disease chronic multifocal osteomyelitis. It is manifested by sterile inflammation of the bones and surrounding soft tissues of the hind limbs and tail. The disease development is propelled by elevated production of IL-1β and reactive oxygen species by neutrophil granulocytes. However, the molecular mechanisms linking PSTPIP2 and these pathways have not been established. Candidate proteins potentially involved in these mechanisms include PSTPIP2 binding partners, PEST family phosphatases (PEST-PTPs) and phosphoinositide phosphatase SHIP1. METHODS: To address the role of these proteins in PSTPIP2-mediated control of inflammation, we have generated mouse strains in which PEST-PTP or SHIP1 binding sites in PSTPIP2 have been disrupted. In these mouse strains, we followed disease symptoms and various inflammation markers. RESULTS: Our data show that mutation of the PEST-PTP binding site causes symptomatic disease, whereas mice lacking the SHIP1 interaction site remain asymptomatic. Importantly, both binding partners of PSTPIP2 contribute equally to the control of IL-1β production, while PEST-PTPs have a dominant role in the regulation of reactive oxygen species. In addition, the interaction of PEST-PTPs with PSTPIP2 regulates the production of the chemokine CXCL2 by neutrophils. Its secretion likely creates a positive feedback loop that drives neutrophil recruitment to the affected tissues. CONCLUSIONS: We demonstrate that PSTPIP2-bound PEST-PTPs and SHIP1 together control the IL-1β pathway. In addition, PEST-PTPs have unique roles in the control of reactive oxygen species and chemokine production, which in the absence of PEST-PTP binding to PSTPIP2 shift the balance towards symptomatic disease.

• Keywords
• PEST-family phosphatases, PSTPIP2, SHIP1, autoinflammation, chronic multifocal osteomyelitis, neutrophils,
• MeSH
• Adaptor Proteins, Signal Transducing * metabolism   MeSH
• Cytoskeletal Proteins * metabolism   MeSH
• Mice MeSH
• Neutrophils * MeSH
• Osteomyelitis MeSH
• Reactive Oxygen Species metabolism   MeSH
• Inflammation MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adaptor Proteins, Signal Transducing * MeSH
• Cytoskeletal Proteins * MeSH
• Pstpip2 protein, mouse MeSH Browser
• Reactive Oxygen Species MeSH

A number of human autoinflammatory diseases manifest with severe inflammatory bone destruction. Mouse models of these diseases represent valuable tools that help us to understand molecular mechanisms triggering this bone autoinflammation. The Pstpip2cmo mouse strain is among the best characterized of these; it harbors a mutation resulting in the loss of adaptor protein PSTPIP2 and development of autoinflammatory osteomyelitis. In Pstpip2cmo mice, overproduction of interleukin-1β (IL-1β) and reactive oxygen species by neutrophil granulocytes leads to spontaneous inflammation of the bones and surrounding soft tissues. However, the upstream signaling events leading to this overproduction are poorly characterized. Here, we show that Pstpip2cmo mice deficient in major regulator of Src-family kinases (SFKs) receptor-type protein tyrosine phosphatase CD45 display delayed onset and lower severity of the disease, while the development of autoinflammation is not affected by deficiencies in Toll-like receptor signaling. Our data also show deregulation of pro-IL-1β production by Pstpip2cmo neutrophils that are attenuated by CD45 deficiency. These data suggest a role for SFKs in autoinflammation. Together with previously published work on the involvement of protein tyrosine kinase spleen tyrosine kinase, they point to the role of receptors containing immunoreceptor tyrosine-based activation motifs, which after phosphorylation by SFKs recruit spleen tyrosine kinase for further signal propagation. We propose that this class of receptors triggers the events resulting in increased pro-IL-1β synthesis and disease initiation and/or progression.

• Keywords
• CD45, PSTPIP2, PTPRC, autoinflammation, chronic recurrent multifocal osteomyelitis,
• MeSH
• Adaptor Proteins, Signal Transducing genetics   immunology   MeSH
• Leukocyte Common Antigens genetics   immunology   MeSH
• Cytoskeletal Proteins genetics   immunology   MeSH
• Diabetes Mellitus, Type 1 genetics   immunology   pathology   MeSH
• Interleukin-1beta genetics   immunology   MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Neutrophils immunology   pathology   MeSH
• Osteomyelitis genetics   immunology   pathology   MeSH
• Signal Transduction genetics   immunology   MeSH
• Severity of Illness Index MeSH
• Toll-Like Receptors genetics   immunology   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adaptor Proteins, Signal Transducing MeSH
• Leukocyte Common Antigens MeSH
• Cytoskeletal Proteins MeSH
• IL1B protein, mouse MeSH Browser
• Interleukin-1beta MeSH
• Pstpip2 protein, mouse MeSH Browser
• Ptprc protein, mouse MeSH Browser
• Toll-Like Receptors MeSH

Although signal transduction by immunoreceptors such as the T cell antigen receptor (TCR), B cell antigen receptor (BCR), and Fc receptors uses the same schematic and similar molecules, the threshold and the fine-tuning are set differently for each receptor. One manifestation of these differences is that inhibition of Src family kinases (SFK) blocks TCR but not BCR signaling. SFKs are key kinases phosphorylating immunoreceptor tyrosine-based activation motifs (ITAM) in both these receptors. However, it has been proposed that in B cells, downstream kinase SYK can phosphorylate ITAM sequences independently of SFK, allowing it to compensate for the loss of SFK activity, whereas its T cell paralog ZAP-70 is not capable of this compensation. To test this proposal, we examined signaling in SYK- and ZAP-70-deficient B and T cell lines expressing SYK or ZAP-70. We also analyzed signal transduction in T cells expressing BCR or B cells expressing part of the TCR complex. We show that when compared with ZAP-70, SYK lowered the threshold for SFK activity necessary to initiate antigen receptor signaling in both T and B cells. However, neither SYK nor ZAP-70 were able to initiate signaling independently of SFK. We further found that additional important factors are involved in setting this threshold. These include differences between the antigen receptor complexes themselves and the spatial separation of the key transmembrane adaptor protein LAT from the TCR. Thus, immunoreceptor sensing of SFK activity is a complex process regulated at multiple levels.

• Keywords
• B-cell receptor, SYK-family kinases, Src-family kinases, T-cell receptor (TCR), adaptor protein, calcium, inhibitor, receptor regulation, signal transduction, tyrosine-protein kinase (tyrosine kinase),
• MeSH
• B-Lymphocytes metabolism   MeSH
• Jurkat Cells MeSH
• Syk Kinase genetics   metabolism   MeSH
• Humans MeSH
• ZAP-70 Protein-Tyrosine Kinase genetics   metabolism   MeSH
• Receptors, Antigen, B-Cell genetics   metabolism   MeSH
• Receptors, Antigen, T-Cell genetics   metabolism   MeSH
• Signal Transduction * MeSH
• src-Family Kinases genetics   metabolism   MeSH
• T-Lymphocytes metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Syk Kinase MeSH
• ZAP-70 Protein-Tyrosine Kinase MeSH
• Receptors, Antigen, B-Cell MeSH
• Receptors, Antigen, T-Cell MeSH
• src-Family Kinases MeSH
• SYK protein, human MeSH Browser
• ZAP70 protein, human MeSH Browser