Serglycin proteoglycan deletion induces defects in platelet aggregation and thrombus formation in mice

Abstract

Serglycin (SG), the hematopoietic cell secretory granule proteoglycan, is crucial for storage of specific secretory proteins in mast cells, neutrophils, and cytotoxic T lymphocytes. We addressed the role of SG in platelets using SG-/- mice. Wild-type (WT) but not SG-/- platelets contained chondroitin sulfate proteoglycans. Electron microscopy revealed normal alpha-granule structure in SG-/- platelets. However, SG-/- platelets and megakaryocytes contained unusual scroll-like membranous inclusions, and SG-/- megakaryocytes showed extensive emperipolesis of neutrophils. SG-/- platelets had reduced ability to aggregate in response to low concentrations of collagen or PAR4 thrombin receptor agonist AYPGKF, and reduced fibrinogen binding after AYPGKF, but aggregated normally to ADP. 3H-serotonin and ATP secretion were greatly reduced in SG-/- platelets. The alpha-granule proteins platelet factor 4, beta-thromboglobulin, and platelet-derived growth factor were profoundly reduced in SG-/- platelets. Exposure of P-selectin and alphaIIb after thrombin treatment was similar in WT and SG-/- platelets. SG-/- mice exhibited reduced carotid artery thrombus formation after exposure to FeCl3. This study demonstrates that SG is crucial for platelet function and thrombus formation. We propose that SG-/- platelet function deficiencies are related to inadequate packaging and secretion of selected alpha-granule proteins and reduced secretion of dense granule contents critical for platelet activation.

Delayed Contraction of the CD8+ T Cell Response toward Lymphocytic Choriomeningitis Virus Infection in Mice Lacking Serglycin

“…Thus, serglycin has been shown to be crucial for storage of various molecules in different hematopoietic cells: 1) various proteases in mast cells (27,35), 2) elastase in neutrophils (41), 3) platelet factor 4 in platelets (42), and 4) GrB in Con A-induced CTLs (24). Considering the importance of serglycin in regulating secretory granule content and morphology in in vitro-activated CTLs (24), we investigated in this study the possibility that serglycin may be important for antiviral responses in vivo.…”

Heparan Sulfate Proteoglycans

“…Serglycin Null allele: viable; secretory granule defects in mast cells (Abrink et al 2004); dense core formation is defective in mast cell granules (Henningsson et al 2006); defective secretory granule maturation and granzyme B storage in cytotoxic T cells (Grujic et al 2005); no effect on macrophages (Zernichow et al 2006); platelets and megakaryocytes contain unusual scroll-like membranous inclusions (Woulfe et al 2008); enlargement of multiple lymphoid organs, decrease in the proportion of CD4 þ cells, more pronounced airway inflammatory response in older mice (Wernersson et al 2009); increased virulence of Klebsiella pneumoniae (Niemann et al 2007); defective regulation of antiviral CD8 þ T-cell responses (Grujic et al 2008). Agrn Agrin Null allele: embryonic lethal; reduced number, size, and density of postsynaptic acetylcholine receptor aggregates in muscles; abnormal intramuscular nerve branching and presynaptic differentiation (Gautam et al 1996(Gautam et al ,1999; smaller brains (Serpinskaya et al 1999); abnormal development of interneuronal synapses (Gingras et al 2007); increased resistance to excitotoxic injury (Hilgenberg et al 2002); reduced number of cortical presynaptic and postsynaptic specializations (Ksiazek et al 2007).…”

Serglycin: A Structural and Functional Chameleon with Wide Impact on Immune Cells

“…In contrast, the storage of other azurophil granule compounds, including cathepsin G and proteinase 3, was unaffected by the absence of serglycin (24). In platelets, the absence of serglycin has multiple effects, including severely defective storage of CXCL4, CXCL7, and platelet-derived growth factor (22).…”

“…Serglycin was originally regarded as a hematopoietic cell proteoglycan species (29), being highly expressed by several hematopoietic cell types, such as MCs, NK cells, CTLs, platelets, and macrophages (18,22,26,34). However, serglycin is also expressed by a number of nonhematopoietic cell types, including endothelial cells (21), chondrocytes (35), and smooth muscle cells (36).…”

“…A dependence on serglycin for dense core formation was also seen in the cytolytic granules of CTLs (18), whereas, in contrast, no morphological effects of serglycin deficiency were seen in either macrophages (26) or neutrophils (24). In platelets, the absence of serglycin was associated with formation of unusual cigar-like membrane inclusions, reminiscent of the pathology seen in certain platelet-related disorders (22).…”