LRP1 and Stroke: The activity of tPA in fibrinolysis and stroke is based on its function as a protease16; however, recombinant tPA also interacts with cellular receptors such as the N-methyl-D-aspartate Receptor (NMDA-R)17,18 and LDL Receptor-related Protein-1 (LRP1)19 to mediate changes in cell physiology that are independent of its protease activity and potentially relevant to the challenges of stem cell therapy.