Human ␣-defensins are evolutionarily conserved effectors of the innate immune response with broadly acting antibacterial activity. Their role in antiviral immunity is less well understood. We previously showed that these antimicrobial peptides are potent inhibitors of human adenovirus infection. Based on biochemical studies and indirect evidence from confocal microscopy, we proposed that defensins bind to and stabilize the virus capsid and neutralize infection by preventing the release of the endosomalytic protein VI. To determine whether defensin action also restricts exposure of the viral genome, we developed a system to evaluate adenovirus uncoating during cell entry by monitoring the exposure of BrdU-labeled viral genomes. This assay allowed us to determine the kinetics of uncoating of virus particles in single cells. Using this assay, we now provide direct evidence that human ␣-defensins block adenovirus infection by preventing uncoating during cell entry.

These findings identify mitochondrial CaMKII as a key regulator of mitochondrial Ca uptake via MCU, thereby controlling mitochondrial translocation and VSMC migration after vascular injury.

The role of the mitochondrial Ca2+ uniporter (MCU) in physiologic cell proliferation remains to be defined. Here, we demonstrated that the MCU was required to match mitochondrial function to metabolic demands during cell cycling. During the G1/S transition (the cycle phase with the highest mitochondrial ATP output), mitochondrial fusion, oxygen consumption and Ca2+ uptake increased in wild-type cells, but not in cells lacking MCU. In proliferating wild-type control cells, the addition of the growth factors promoted the activation of the Ca2+/calmodulin-dependent kinase II (CaMKII) and the phosphorylation of the mitochondrial fission factor Drp1 at Ser616. The lack of the MCU was associated with baseline activation of CaMKII, mitochondrial fragmentation due to increased Drp1 phosphorylation, and impaired mitochondrial respiration and glycolysis. The mitochondrial fission/fusion ratio and proliferation in MCU-deficient cells recovered after MCU restoration or inhibition of mitochondrial fragmentation or of CaMKII in the cytosol. Our data highlight a key function for the MCU in mitochondrial adaptation to the metabolic demands during cell cycle progression. Cytosolic CaMKII and the MCU participate in a regulatory circuit whereby mitochondrial Ca2+ uptake affects cell proliferation through Drp1.

Activation of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) and reactive oxygen species (ROS) promote neointimal hyperplasia after vascular injury. CaMKII can be directly activated by ROS through oxidation. In this study, we determined whether abolishing the oxidative activation site of CaMKII alters vascular smooth muscle cell (VCMC) proliferation, migration and apoptosis in vitro and neointimal formation in vivo. VSMC isolated from a knock-in mouse with oxidation-resistant CaMKIIδ (CaMKII M2V) displayed similar proliferation but decreased migration and apoptosis. Surprisingly, ROS production and expression of the NADPH oxidase subunits p47 and p22 were decreased in M2V VSMC, whereas superoxide dismutase 2 protein expression was upregulated. In vivo, after carotid artery ligation, no differences in neointimal size or remodeling were observed. In contrast to VSMC, CaMKII expression and autonomous activity were significantly higher in M2V compared to WT carotid arteries, suggesting an autoregulatory mechanism determines CaMKII activity in vivo. Our findings demonstrate that preventing oxidative activation of CaMKII decreases migration and apoptosis in vitro and suggest that CaMKII regulates ROS production. Our study presents novel evidence that CaMKII expression in vivo is regulated by a negative feedback loop following oxidative activation.

ObjectiveSustained hemodynamic stress mediated by high blood flow promotes arteriogenesis, the outward remodeling of existing arteries. Here, we examined whether Ca2+/calmodulin-dependent kinase II (CaMKII) regulates arteriogenesis.Methods and ResultsLigation of the left common carotid led to an increase in vessel diameter and perimeter of internal and external elastic lamina in the contralateral, right common carotid. Deletion of CaMKIIδ (CaMKIIδ−/−) abolished this outward remodeling. Carotid ligation increased CaMKII expression and was associated with oxidative activation of CaMKII in the adventitia and endothelium. Remodeling was abrogated in a knock-in model in which oxidative activation of CaMKII is abolished. Early after ligation, matrix metalloproteinase 9 (MMP9) was robustly expressed in the adventitia of right carotid arteries of WT but not CaMKIIδ−/− mice. MMP9 mainly colocalized with adventitial macrophages. In contrast, we did not observe an effect of CaMKIIδ deficiency on other proposed mediators of arteriogenesis such as expression of adhesion molecules or smooth muscle proliferation. Transplantation of WT bone marrow into CaMKIIδ−/− mice normalized flow-mediated remodeling.ConclusionCaMKIIδ is activated by oxidation under high blood flow conditions and is required for flow-mediated remodeling through a mechanism that includes increased MMP9 expression in bone marrow-derived cells invading the arterial wall.