TY - JOUR
T1 - The α-granule proteome
T2 - Novel proteins in normal and ghost granules in gray platelet syndrome
AU - Maynard, D. M.
AU - Heijnen, H. F.G.
AU - Gahl, W. A.
AU - Gunay-Aygun, M.
PY - 2010/8
Y1 - 2010/8
N2 - Background: Deficiencies in granule-bound substances in platelets cause congenital bleeding disorders known as storage pool deficiencies. For disorders such as gray platelet syndrome (GPS), in which thrombocytopenia, enlarged platelets and a paucity of α-granules are observed, only the clinical and histologic states have been defined. Objectives: In order to understand the molecular defect in GPS, the α-granule fraction protein composition from a normal individual was compared with that of a GPS patient by mass spectrometry (MS). Methods: Platelet organelles were separated by sucrose gradient ultracentrifugation. Proteins from sedimented fractions were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis, reduced, alkylated, and digested with trypsin. Peptides were analyzed by liquid chromatography-tandem MS. M. ascot was used for peptide/protein identification and to determine peptide false-positive rates. M. assS. ieve was used to generate and compare parsimonious lists of proteins. Results: As compared with control, the normalized peptide hits (NPHs) from soluble, biosynthetic α-granule proteins were markedly decreased or undetected in GPS platelets, whereas the NPHs from soluble, endocytosed α-granule proteins were only moderately affected. The NPHs from membrane-bound α-granule proteins were similar in normal platelets and GPS platelets, although P-selectin and Glut3 were slightly decreased, consistent with immunoelectron microscopy findings in resting platelets. We also identified proteins not previously known to be decreased in GPS, including latent transforming growth factor-β-binding protein 1(LTBP1), a component of the transforming growth factor-β (TGF-β) complex. Conclusions: Our results support the existence of 'ghost granules' in GPS, point to the basic defect in GPS as failure to incorporate endogenously synthesized megakaryocytic proteins into α-granules, and identify specific new proteins as α-granule inhabitants.
AB - Background: Deficiencies in granule-bound substances in platelets cause congenital bleeding disorders known as storage pool deficiencies. For disorders such as gray platelet syndrome (GPS), in which thrombocytopenia, enlarged platelets and a paucity of α-granules are observed, only the clinical and histologic states have been defined. Objectives: In order to understand the molecular defect in GPS, the α-granule fraction protein composition from a normal individual was compared with that of a GPS patient by mass spectrometry (MS). Methods: Platelet organelles were separated by sucrose gradient ultracentrifugation. Proteins from sedimented fractions were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis, reduced, alkylated, and digested with trypsin. Peptides were analyzed by liquid chromatography-tandem MS. M. ascot was used for peptide/protein identification and to determine peptide false-positive rates. M. assS. ieve was used to generate and compare parsimonious lists of proteins. Results: As compared with control, the normalized peptide hits (NPHs) from soluble, biosynthetic α-granule proteins were markedly decreased or undetected in GPS platelets, whereas the NPHs from soluble, endocytosed α-granule proteins were only moderately affected. The NPHs from membrane-bound α-granule proteins were similar in normal platelets and GPS platelets, although P-selectin and Glut3 were slightly decreased, consistent with immunoelectron microscopy findings in resting platelets. We also identified proteins not previously known to be decreased in GPS, including latent transforming growth factor-β-binding protein 1(LTBP1), a component of the transforming growth factor-β (TGF-β) complex. Conclusions: Our results support the existence of 'ghost granules' in GPS, point to the basic defect in GPS as failure to incorporate endogenously synthesized megakaryocytic proteins into α-granules, and identify specific new proteins as α-granule inhabitants.
KW - Gray platelet syndrome
KW - LTBP1
KW - Mass spectrometry
KW - Platelet
KW - α-granule
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U2 - 10.1111/j.1538-7836.2010.03932.x
DO - 10.1111/j.1538-7836.2010.03932.x
M3 - Article
C2 - 20524979
AN - SCOPUS:77958539006
SN - 1538-7933
VL - 8
SP - 1786
EP - 1796
JO - Journal of Thrombosis and Haemostasis
JF - Journal of Thrombosis and Haemostasis
IS - 8
ER -