The small guanine-nucleotide-binding protein Rap1 plays a key role in platelet aggregation and hemostasis, and we recently identified Rap1GAP2 as the only GTPase-activating protein of Rap1 in platelets. In search of Rap1GAP2-associated proteins, we performed yeast-2-hybrid screening and found synaptotagmin-like protein 1 (Slp1) as a new binding partner. We confirmed the interaction of Rap1GAP2 ...

Studies have demonstrated significant heterogeneity in neutrophil granule morphology and physical density. Using cytochemical methods to localize peroxidase and vicinal glycol containing complex carbohydrates we examined the heterogeneity of neutrophil granules from intact human neutrophil granules in 13 isolated granule density fractions, calcium ionophore A23187 treated neutrophils and neutro...

We have generated a monoclonal antibody (mAb) 5E10 which recognizes an antigen localized to dense core vesicles (DCVs) in the atrial gland of Aplysia californica. mAb5E10 immunoprecipitates an abundant 57-kDa glycoprotein (atrial gland granule-specific antigen, AGSA) which is a soluble component of atrial gland DCVs. Electron microscopy reveals that AGSA immunoreactivity is restricted to the re...

In a recent study, we showed that granulocyte-macrophage colony-stimulating factor (GM-CSF) and supernatants from partially stimulated platelets undergoing selective alpha-granule release synergistically enhanced polymorphonuclear leukocyte (PMN) response to N-formyl-methionyl-leucyl-phenylalanine (fMLP). The active factor released from platelet alpha-granules was identified as platelet factor ...

Toxoplasma gondii possesses unique secretory organelles, which synchronously release proteins during and after invasion. One of these organelles, the dense granules, secrete proteins after invasion which are thought to be important in development of the parasite throughout all stages of its life cycle. Dense granule protein 3 (GRA3) is a 30 kDa protein localized to the intravacuolar network and...

Platelet granules are unique among secretory vesicles in both their content and their life cycle. Platelets contain three major granule types-dense granules, α-granules, and lysosomes-although other granule types have been reported. Dense granules and α-granules are the most well-studied and the most physiologically important. Platelet granules are formed in large, multilobulated cells, termed ...