Casein Kinase 2α is a crucial regulator of GPVI-mediated in vivo arterial thrombus formation in macro- and microcirculation

Mailin-Christin Manke (Tübingen)1, M. Fischer (Tübingen)1, F. Kollotzek (Tübingen)1, J. P. Schütte (Tübingen)1, P. Münzer (Tübingen)1, M. Gawaz (Tübingen)1, O. Borst (Tübingen)1

1Universitätsklinikum Tübingen Innere Medizin III, Kardiologie und Angiologie Tübingen, Deutschland


Background: Cardiovascular diseases such as myocardial infarction and ischemic stroke depend decisively on platelet functions such as adhesion, secretion and thrombus formation. Since the activation of platelets is regulated by a wide variety of intracellular, phosphorylation-dependent signaling cascades, highly expressed kinases in platelets play a pivotal role in platelet activation. One of these kinases represents the tetrameric serine/threonine kinase casein kinase 2 (CK2), which consists of two regulatory β and two catalytic α or α’ subunits respectively. While deficiency of the regulatory β subunit is characterized by impaired thrombopoiesis and platelet function, nothing is yet known about the role of the α subunit in platelet activation and subsequent in vivo thrombus formation in arterial macro- and microcirculation.

Aims: The present study examined the effects of CK2α-dependent platelet activation as well as macro- and microcirculatory thrombus formation.

Methods and Results: With the use of platelet-specific CK2α-deficient mice (csnk2αPf4∆/Pf4∆) and wild-type littermates (csnk2αlox/lox), flow cytometric analysis demonstrated disturbed integrin αIIbβ3 activation and P-selectin surface exposure in platelets from csnk2αPf4∆/Pf4∆ mice upon stimulation with GPVI-specific platelet agonist collagen-related peptide (CRP). Csnk2αPf4∆/Pf4∆ mice showed also diminished platelet spreading on a fibrinogen-coated surface and serial spectrofluorimetric measurements detected a significantly decreased intracellular Ca2+ release and extracellular Ca2+ influx after CRP stimulation in CK2α-deficient platelets. In addition, CRP-dependent platelet aggregation and secretion were abrogated in Csnk2α-deficient platelets. Consistent with these results, we observed a defective in vitro arterial thrombus formation in a flow chamber using a collagen-coated surface and varying shear rates. These results are in line with in vivo models since FeCl3-induced injury in carotid and mesenteric arteries, which represent macro- or microcirculation respectively, showed decreased thrombus formation in csnk2αPf4∆/Pf4∆ mice when compared to csnk2αlox/lox mice. However, in a tail tip transection model remarkably no difference between bleeding times in both groups was found, although csnk2α-deficient mice displayed an improved outcome after myocardial ischemia/reperfusion injury.

Conclusions: Our results reveal CK2α as crucial regulator of GPVI-mediated platelet activation and arterial in vivo thrombus formation in macro- and microcirculation. Since the lack of CK2α does not compromise the bleeding time of mice, CK2 could therefore represent a promising new pharmacological target for the treatment of thrombo-occlusive disorders.

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