Phosphatidylethanolamine critically supports internalization of cell-penetrating protein C inhibitor.
Although their contribution remains unclear, lipids may facilitate noncanonical routes of protein internalization into cells such as those used by cell-penetrating proteins. We show that protein C inhibitor (PCI), a serine protease inhibitor (serpin), rapidly transverses the plasma membrane, which persists at low temperatures and enables its nuclear targeting in vitro and in vivo. Cell membrane translocation of PCI necessarily requires phosphatidylethanolamine (PE). In parallel, PCI acts as a lipid transferase for PE. The internalized serpin promotes phagocytosis of bacteria, thus suggesting a function in host defense. Membrane insertion of PCI depends on the conical shape of PE and is associated with the formation of restricted aqueous compartments within the membrane. Gain- and loss-of-function mutations indicate that the transmembrane passage of PCI requires a branched cavity between its helices H and D, which, according to docking studies, precisely accommodates PE. Our findings show that its specific shape enables cell surface PE to drive plasma membrane translocation of cell-penetrating PCI.
Baumgärtner
Petra
P
Vaskuläre Biologie und Hämostase, Institut für Klinische Chemie, 81377 Munich, Germany.
Geiger
Margarethe
M
Zieseniss
Susanne
S
Malleier
Julia
J
Huntington
James A
JA
Hochrainer
Karin
K
Bielek
Edith
E
Stoeckelhuber
Mechthild
M
Lauber
Kirsten
K
Scherfeld
Dag
D
Schwille
Petra
P
Wäldele
Katja
K
Beyer
Klaus
K
Engelmann
Bernd
B
D000818:Animals; D001665:Binding Sites; D001710:Biotin / Q000378:metabolism; D001792:Blood Platelets / Q000737:chemistry / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006098:Granulocytes / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D007962:Leukocytes / Q000473:pathology / Q000648:ultrastructure; D051379:Mice; D009154:Mutation; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects; D011485:Protein Binding; D018046:Protein C Inhibitor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology; D013997:Time Factors
D007457:Iodine Radioisotopes; D010714:Phosphatidylethanolamines; D018046:Protein C Inhibitor; D011994:Recombinant Proteins; D001710:Biotin; D013917:Thrombin