Functional links between Disabled-2 Ser723 phosphorylation and thrombin signaling in human platelets

Area of Science:

• Biochemistry
• Cell Biology
• Hematology

Background:

• Disabled-2 (Dab2) is a platelet protein involved in thrombin signaling in mice.
• The phosphorylation status and function of Dab2 in human platelet activation remain unclear.

Purpose of the Study:

• To investigate Dab2 phosphorylation in thrombin-stimulated human platelets.
• To determine the functional consequences of Dab2 phosphorylation.

Main Methods:

• Mass spectrometry to identify phosphorylation sites.
• Generation of a phospho-specific antibody.
• Use of signaling pathway inhibitors and activators.
• Protein kinase assays and molecular approaches.

Main Results:

• Dab2 is phosphorylated at multiple sites (Ser227, Ser394, Ser401, Ser723) in thrombin-stimulated platelets, with Ser723 showing the most significant increase.
• Protein kinase C phosphorylates Dab2 at Ser723 in a Gαq-dependent manner.
• Ser723 phosphorylation causes dissociation of the Dab2-CIN85 complex, enhancing fibrinogen binding and platelet aggregation.

Conclusions:

• Dab2 Ser723 phosphorylation is a key event in thrombin-induced platelet activation.
• This phosphorylation regulates inside-out signaling, impacting αIIbβ3 activation and ADP release.
• Dab2 plays a newly identified role in thrombin signaling pathways.