Calcium-sensitive calmodulin kinase (CaM kinase) may phosphorylate Drp-1 and contribute to Drp1 activation [186]; however, in PAH PASMCs a CDK1 inhibitor (RO-3396) was more effective than a CamK inhibitor in reducing Drp1 phosphorylation, which suggests that cyclin B-CDK1 is the predominant mediator of Drp1 activation in PAH [21]. Here, CDK1 is linked to pulmonary arterial hypertension.