The F-BAR protein PSTPIP1 controls extracellular matrix degradation and filopodia formation in macrophages

Abstract

Key Points• PSTPIP1 regulates the transition from podosomes to filopodia in macrophages by modulating WASP activity.• The novel PSTPIP1-R405C mutant induces filopodia formation, increases matrix degradation, and is associated with severe pyoderma gangrenosum.PSTPIP1 is a cytoskeletal adaptor and F-BAR protein that has been implicated in autoinflammatory disease, most notably in the PAPA syndrome: pyogenic sterile arthritis, pyoderma gangrenosum, and acne. However, the mechanism by which PSTPIP1 regulates the actin cytoskeleton and contributes to disease pathogenesis remains elusive. Here, we show that endogenous PSTPIP1 negatively regulates macrophage podosome organization and matrix degradation. We identify a novel PSTPIP1-R405C mutation in a patient presenting with aggressive pyoderma gangrenosum. Identification of this mutation reveals that PSTPIP1 regulates the balance of podosomes and filopodia in macrophages. The PSTPIP1-R405C mutation is in the SRC homology 3 (SH3) domain and impairs Wiskott-Aldrich syndrome protein (WASP) binding, but it does not affect interaction with protein-tyrosine phosphatase (PTP)-PEST. Accordingly, WASP inhibition reverses the elevated F-actin content, filopodia formation, and matrix degradation induced by PSTPIP1-R405C. Our results uncover a novel role for PSTPIP1 and WASP in orchestrating different types of actin-based protrusions. Our findings implicate the cytoskeletal regulatory functions of PSTPIP1 in the pathogenesis of pyoderma gangrenosum and suggest that the cytoskeleton is a rational target for therapeutic intervention in autoinflammatory disease. (Blood. 2014;123(17):2703-2714 Introduction Dynamic regulation of the actin cytoskeleton and cell migration is essential for cellular immunity, because leukocytes travel long distances between tissues to perform their effector functions. Indeed, immunodeficiency syndromes, including Wiskott-Aldrich syndrome, leukocyte adhesion deficiency, and warts-hypogammaglobulinemiainfections-myelokathexis syndrome, are secondary to defects in the cytoskeleton and motility of leukocytes.1 Colchicine, which inhibits microtubule polymerization, is used to treat inflammatory conditions, and several other compounds that target cell motility are in development as immunomodulators, which indicates the importance of regulating the cytoskeleton to control immunity and inflammation.2,3 Conversely, neutrophils from patients with the autoinflammatory disease, neonatal onset multisystem inflammatory disease/ Muckle-Wells syndrome, have impaired chemotaxis, which suggests that altered leukocyte migration may also promote a proinflammatory state. 4 While altered leukocyte motility has been established as a cause of immunodeficiency, the role of cytoskeletal dysregulation and altered motility in inflammation and tissue damage remains poorly characterized.Proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1) is a cytoskeleton-associated adaptor and F-BAR domaincontaining protein that is linked to PAPA syndrome, the human inflammatory disea...

HIV-1 reprograms the migration of macrophages

“…26,32,33,53,[58][59][60] Even though the analysis of podosomes is a challenging task in 3D Matrigel, 26,31 we showed that HIV-1-infected and Nef-expressing (Figure 4A-B; data not shown), as defined for 3D podosomes. 26,31,61 The number of these protrusions per cell was increased on HIV-1 infection (8.6 vs 2.7, n .…”

Tools of the trade: podosomes as multipurpose organelles of monocytic cells

“…An R405C amino acid exchange, for example, leads to reduced podosome formation, enhanced numbers of filopodia, and matrix degradation in human macrophages [61]. Interestingly, WASP is also involved in this phenomenon, as the R405C exchange results in impaired WASP binding of PSTPIP1 [61]. It has to be noted that, for both WAS and PAPA syndrome, the activity of WASP or PSTPIP1 is not restricted to podosomes or filopodia, but is likely to affect the whole cytoskeleton.…”

“…Further important aspects include the discovery of podosome dynamics, comprising de novo formation, fusion, fission, and dissolution [38,40,57] and the identification of the podosome proteome, which is in the range of *200 proteins [58], comparable to that of focal adhesions [2] or invadopodia [59]. Moreover, macrophages enabled the discovery of podosomes in a 3D context [60], and also the link to potentially podosomebased diseases [5,61] (see paragraphs on podosomes in 3D environments and on podosome-associated diseases below).…”

Podosomes are disrupted in PAPA syndrome

“…Mice expressing a talin-1 mutant (W359A) that disrupts its binding to the NPxY motif in b 3 were protected from experimental thrombosis without undermining hemostasis by decelerating aIIbb3 activation. 1 I n addition to their essential role in hemostasis, platelets play a crucial role in a pathological thrombus formation, particularly within atherosclerotic arteries subjected to high shear stress. 2 As an initial step in thrombogenesis (or hemostasis), platelets adhere to altered vascular surfaces or exposed subendothelial matrices, then become activated and aggregate each other to grow thrombus (or platelet plug) volume.…”

“…4,5 In this issue of Blood, a novel mutation in the PSTPIP1 gene is described in a patient with PAPA syndrome. 1 The R405C mutation is the first mutation described in the SH3 domain of PSTPIP1. It is distant from the binding domain of PTP-PEST, which normally interacts with PSTPIP1.…”