PSTPIP2, a Protein Associated with Autoinflammatory Disease, Interacts with Inhibitory Enzymes SHIP1 and Csk

Abstract

Mutations in the adaptor protein PSTPIP2 are the cause of the autoinflammatory disease chronic multifocal osteomyelitis in mice. This disease closely resembles the human disorder chronic recurrent multifocal osteomyelitis, characterized by sterile inflammation of the bones and often associated with inflammation in other organs, such as the skin. The most critical process in the disease’s development is the enhanced production of IL-1β. This excessive IL-1β is likely produced by neutrophils. In addition, the increased activity of macrophages, osteoclasts, and megakaryocytes has also been described. However, the molecular mechanism of how PSTPIP2 deficiency results in this phenotype is poorly understood. Part of the PSTPIP2 inhibitory function is mediated by protein tyrosine phosphatases from the proline-, glutamic acid-, serine- and threonine-rich (PEST) family, which are known to interact with the central part of this protein, but other regions of PSTPIP2 not required for PEST-family phosphatase binding were also shown to be indispensable for PSTPIP2 function. In this article, we show that PSTPIP2 binds the inhibitory enzymes Csk and SHIP1. The interaction with SHIP1 is of particular importance because it binds to the critical tyrosine residues at the C terminus of PSTPIP2, which is known to be crucial for its PEST-phosphatase–independent inhibitory effects in different cellular systems. We demonstrate that in neutrophils this region is important for the PSTPIP2-mediated suppression of IL-1β processing and that SHIP1 inhibition results in the enhancement of this processing. We also describe deregulated neutrophil response to multiple activators, including silica, Ab aggregates, and LPS, which is suggestive of a rather generalized hypersensitivity of these cells to various external stimulants.

Development of SH2 probes and pull‐down assays to detect pathogen‐induced, site‐specific tyrosine phosphorylation of the TLR adaptor SCIMP

“…LC‐MS/MS analysis of the pull‐down fraction revealed a number of known and novel Csk binding partners (Figure 4b). In addition to SCIMP itself, Csk‐SH2 bound to proteins like SHIP1, 22 LRP‐1 23 and PLCγ, 24 all previously reported as direct binding partners of Csk. Other proteins in the list identified with high scores include small GTPases or GTPase regulators such as RasL2 and RCC2, 25 thus revealing these proteins as novel Csk targets.…”

SWAP70 Organizes the Actin Cytoskeleton and Is Essential for Phagocytosis

“…Phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P 2 ), which is the predominant phosphoinositide at the plasma membrane (van den Bogaart and ter Beest, 2014), converts into PI(3,4,5)P 3 by the action of PI3-kinases (Greenberg and Grinstein, 2002, Gu et al., 2003, Hoppe and Swanson, 2004, Terebiznik et al., 2002). PI(3,4,5)P 3 is then dephosphorylated by SHIP1 (INPP5D) and SHIP2 (INPPL1), yielding PI(3,4)P 2 (Brooks et al., 2010, Drobek et al., 2015, Fuhler et al., 2012), which in turn is converted into PI(3)P by PI 4-phosphatases. Both SHIP1 and 2 are expressed by human monocyte-derived dendritic cells (Figure S2A).…”

NLRP3 inflammasome plays a redundant role with caspase 8 to promote IL-1β–mediated osteomyelitis

“…The F-bar domain of PSTPIP2 has been known to interact with phosphatidylinositol bisphosphate, whereas its C-terminal domain binds protein tyrosine phosphatases of the PEST (a domain rich in proline, glutamic acid, serine, and threonine) family (5)(6)(7). Recent studies have shown that PSTPIP2 can also interact with inhibitory enzymes CsK and SHIP1 (8). Whereas human patients with genetic mutations in the PSTPIP2 gene have not been identified, missense L98P mutation in the gene Pstpip2 in mice results in severe autoinflammatory disease of the bones that mimics CRMO in humans and thus these mice are referred to as Pstpip2 cmo mice (9)(10)(11).…”