Mechanism of Enhanced Cellular Uptake and Cytosolic Retention of MK2 Inhibitory Peptide Nano-polyplexes
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Electrostatic complexation of a cationic MAPKAP kinase 2 inhibitory (MK2i) peptide with the anionic, pH-responsive polymer poly(propylacrylic acid) (PPAA) yields MK2i nano-polyplexes (MK2i-NPs) that significantly increase peptide uptake and intracellular retention. This study focused on elucidating the mechanism of MK2i-NP cellular uptake and intracellular trafficking in vascular smooth muscle cells. Small molecule inhibition of various endocytic pathways showed that MK2i-NP cellular uptake involves both macropinocytosis and clathrin mediated endocytosis, whereas the free peptide exclusively utilizes clathrin mediated endocytosis for cell entry. Scanning electron microscopy studies revealed that MK2i-NPs, but not free MK2i peptide, induce cellular membrane ruffling consistent with macropinocytosis. TEM confirmed that MK2i-NPs induce macropinosome formation and achieve MK2i endo-lysosomal escape and cytosolic delivery. Finally, a novel technique based on recruitment of Galectin-8-YFP was utilized to demonstrate that MK2i-NPs cause endosomal disruption within 30 min of uptake. These new insights on the relationship between NP physicochemical properties and cellular uptake and trafficking can potentially be applied to further optimize the MK2i-NP system and more broadly toward the rational engineering of nano-scale constructs for the intracellular delivery of biologic drugs.
KeywordsDrug delivery Nanoparticle Endosome escape pH-responsive polymer Macropinocytosis Vascular therapeutic
We thank Dr. Felix Randow and Dr. Bob Weinburg for kind gifts of plasmids via AddGene.com. We thank Dr. Janice Williams for imaging support and electron microscopy expertise. Confocal imaging, transmission electron microscopy, and scanning electron microscopy were performed in part through the use of the Vanderbilt University Medical Center Cell Imaging Shared Resource (supported by NIH Grants CA68485, DK20593, DK58404, DK59637 and EY08126). Dynamic light scattering was conducted at the Vanderbilt Institute of Nanoscale Sciences and Engineering. This work was supported by the American Heart Association (11SDG4890030), National Institutes of Health/National Heart, Lung, and Blood Institute (R21 HL110056 and R01 HL122347), and a National Science Foundation Graduate Research Fellowship to K.V.K. (0909667 and 1445197).
Conflict of Interest
KVK, BCE, CMB, and CLD report grant support from the National Institutes of Health and the American Heart Association; KVK additionally reports grant support from National Science Foundation Graduate Research Fellowship Program. During the conduct of the study, authors disclose non-financial support from Moerae Matrix, Inc., outside the submitted work. CMB is chief scientific officer and a shareholder of Moerae Matrix, Inc. BCE, CMB, and CLD are inventors listed on patent PCT/US2014/033873, licensed by Moerae Matrix, Inc. MK2i is known commercially known as MMI-0100 and is being developed by Moerae Matrix, Inc. for clinical use (ClinicalTrials.gov Identifier: NCT02515396).
No human or animal studies were carried out by the authors for the completion of this work.
Supplementary material 1 (MP4 27623 kb)
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