TY - JOUR
T1 - Platelet α-granule cargo packaging and release are affected by the luminal proteoglycan, serglycin
AU - Chanzu, Harry
AU - Lykins, Joshua
AU - Wigna-Kumar, Subershan
AU - Joshi, Smita
AU - Pokrovskaya, Irina
AU - Storrie, Brian
AU - Pejler, Gunnar
AU - Wood, Jeremy P.
AU - Whiteheart, Sidney W.
N1 - Publisher Copyright:
© 2021 International Society on Thrombosis and Haemostasis
PY - 2021/4
Y1 - 2021/4
N2 - Background: Serglycin (SRGN) is an intragranular, sulfated proteoglycan in hematopoietic cells that affects granule composition and function. Objective: To understand how SRGN affects platelet granule packaging, cargo release, and extra-platelet microenvironments. Methods: Platelets and megakaryocytes from SRGN−/− mice were assayed for secretion kinetics, cargo levels, granule morphology upon activation, and receptor shedding. Results: Metabolic, 35SO4 labeling identified SRGN as a major sulfated macromolecule in megakaryocytes. SRGN colocalized with α-granule markers (platelet factor 4 [PF4], von Willebrand factor [VWF], and P-selectin), but its deletion did not affect α-granule morphology or number. Platelet α-granule composition was altered, with a reduction in basic proteins (pI ≥8; e.g., PF4, SDF-1, angiogenin) and constitutive release of PF4 from SRGN−/− megakaryocytes. P-Selectin, VWF, and fibrinogen were unaffected. Serotonin (5-HT) uptake and β-hexosaminidase (HEXB) were slightly elevated. Thrombin-induced exocytosis of PF4 from platelets was defective; however, release of RANTES/CCL5 was normal and osteopontin secretion was more rapid. Release of 5-HT and HEXB (from dense granules and lysosomes, respectively) were unaffected. Ultrastructural studies showed distinct morphologies in activated platelets. The α-granule lumen of SRGN−/− platelet had a grainy staining pattern, whereas that of wild-type granules had only fibrous material remaining. α-Granule swelling and decondensation were reduced in SRGN−/− platelets. Upon stimulation of platelets, a SRGN/PF4 complex was released in a time- and agonist-dependent manner. Shedding of GPVI from SRGN−/− platelets was modestly enhanced. Shedding of GP1b was unaffected. Conclusion: The polyanionic proteoglycan SRGN influences α-granule packaging, cargo release, and shedding of platelet membrane proteins.
AB - Background: Serglycin (SRGN) is an intragranular, sulfated proteoglycan in hematopoietic cells that affects granule composition and function. Objective: To understand how SRGN affects platelet granule packaging, cargo release, and extra-platelet microenvironments. Methods: Platelets and megakaryocytes from SRGN−/− mice were assayed for secretion kinetics, cargo levels, granule morphology upon activation, and receptor shedding. Results: Metabolic, 35SO4 labeling identified SRGN as a major sulfated macromolecule in megakaryocytes. SRGN colocalized with α-granule markers (platelet factor 4 [PF4], von Willebrand factor [VWF], and P-selectin), but its deletion did not affect α-granule morphology or number. Platelet α-granule composition was altered, with a reduction in basic proteins (pI ≥8; e.g., PF4, SDF-1, angiogenin) and constitutive release of PF4 from SRGN−/− megakaryocytes. P-Selectin, VWF, and fibrinogen were unaffected. Serotonin (5-HT) uptake and β-hexosaminidase (HEXB) were slightly elevated. Thrombin-induced exocytosis of PF4 from platelets was defective; however, release of RANTES/CCL5 was normal and osteopontin secretion was more rapid. Release of 5-HT and HEXB (from dense granules and lysosomes, respectively) were unaffected. Ultrastructural studies showed distinct morphologies in activated platelets. The α-granule lumen of SRGN−/− platelet had a grainy staining pattern, whereas that of wild-type granules had only fibrous material remaining. α-Granule swelling and decondensation were reduced in SRGN−/− platelets. Upon stimulation of platelets, a SRGN/PF4 complex was released in a time- and agonist-dependent manner. Shedding of GPVI from SRGN−/− platelets was modestly enhanced. Shedding of GP1b was unaffected. Conclusion: The polyanionic proteoglycan SRGN influences α-granule packaging, cargo release, and shedding of platelet membrane proteins.
KW - exocytosis
KW - granule biogenesis
KW - megakaryocytes
KW - secretion
KW - shedding
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U2 - 10.1111/jth.15243
DO - 10.1111/jth.15243
M3 - Article
C2 - 33448622
AN - SCOPUS:85100538192
SN - 1538-7933
VL - 19
SP - 1082
EP - 1095
JO - Journal of Thrombosis and Haemostasis
JF - Journal of Thrombosis and Haemostasis
IS - 4
ER -