Endothelial protein C receptor-assisted transport of activated protein C across the mouse blood-brain barrier.
Activated protein C (APC), a serine-protease with anticoagulant, anti-inflammatory, and cytoprotective activities, is neuroprotective and holds potential to treat different neurologic disorders. It is unknown whether APC crosses the blood-brain barrier (BBB) to reach its therapeutic targets in the brain. By using a brain vascular perfusion technique, we show that (125)I-labeled plasma-derived mouse APC enters the brain from cerebrovascular circulation by a concentration-dependent mechanism. The permeability surface area product of (125)I-APC (0.1 nmol/L) in different forebrain regions ranged from 3.11 to 4.13 microL/min/g brain. This was approximately 80- to 110-fold greater than for (14)C-inulin, a simultaneously infused reference tracer. The K(m) value for APC BBB cortical transport was 1.6+/-0.2 nmol/L. Recombinant APC variants with reduced anticoagulant activity, 5A-APC and 3K3A-APC, but not protein C, exhibited high affinity for the APC BBB transport system. Blockade of APC-binding site on endothelial protein C receptor (EPCR), but not blockade of its protease-activated receptor-1 (PAR1) catalytic site, inhibited by >85% APC entry into the brain. APC brain uptake was reduced by 64% in severely deficient EPCR mice, but not in PAR1 null mice. These data suggest that APC and its variants with reduced anticoagulant activity cross the BBB via EPCR-mediated saturable transport.
Deane
Rashid
R
Department of Neurosurgery, Center for Neurodegenerative and Vascular Brain Disorders, University of Rochester Medical Center, Rochester, New York 14642, USA.
LaRue
Barbra
B
Sagare
Abhay P
AP
Castellino
Francis J
FJ
Zhong
Zhihui
Z
Zlokovic
Berislav V
BV
D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D000074283:Endothelial Protein C Receptor; D004789:Enzyme Activation; D006023:Glycoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011486:Protein C / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D011956:Receptors, Cell Surface
D000074283:Endothelial Protein C Receptor; D006023:Glycoproteins; C080248:Procr protein, mouse; D011486:Protein C; D011956:Receptors, Cell Surface