Major Constituents of Alpha (α) Granules of Platelets

• α-granules are one of 4 types of granules in Platelets
• The other 3 include → Dense granules, Lysosomes & Peroxisomes 
• There are approximately 80 α-granules per platelet

Major Constituents of  α-granules are as per the following table:

Physiological role	Constituents of α-granules
For platelet aggregation	VWF, FI, Fibronectin
For irreversible aggregation	Thrombospondin
For Coagulation/anticoagulation	FI, FV, FXI, TAFI, AT, PS
For fibrinolysis	PGL, PAI-1, α2-antiplasmin
Membrane proteins	GPIIb/IIIa, P-selectin, CD40L
EC activation	TGF-β
For leukocyte recruitment	PH4, β-Thromboglobulin, ENA78, SDF-1α, CCL5
Growth factors	EGF, FGF, HFH, IGH-1, PDGF
For angiogenesis/inhibition	VEGF-A, VEGF-C, PDGF, Endostatin, Angiostatin
Bacterial killing	Microbial proteins
Immune molecules	IgG, C3 & Cd precursors, C1 inhibitor, Factor H
Proteases	Protease Nexin II
Matrix breakdown	MMP-2, MMP-9
Others	Amyloid β-protein precursor, Gas6