Our group manipulates cellular membranes to facilitate a variety of cell biology, biotechnology, and therapeutic applications. We currently have three main foci: developing cellular delivery tools that can cross biological membranes to carry useful cargos into cells; using these tools to develop new ways to probe how cells work; and understanding how human cells communicate with one another by exchanging small vesicles filled with proteins and nucleic acids.

Cellular delivery

We develop reagents that can cross membranes, penetrate cells, and deliver useful macromolecules inside human cells. These delivery systems include cell-penetrating peptides (CPPs); small-molecule modulators of membranes; artificial viruses that can deliver gene-editing tools into human cells and plants; and nanocages that encapsulate hard-to-handle drugs. For each, we develop chemical synthesis protocols, establish structure-activity relationships, and study their mechanism of action using biochemical and cellular assays. Through this work, we have uncovered several cellular gateways that allow access to the interior space of cells. Specifically, we have developed reagents that are remarkably efficient at entering cells by escaping the endocytic pathway.

J. Allen, K. Najjar, A. Erazo-Oliveras, H. M. Kondow-McConaghy, D. J. Brock, K. Graham, E. C. Hager, A. L. J. Marschall, S. Dubel, R. L. Juliano, J. P. Pellois, Cytosolic delivery of macromolecules in live human cells using the combined endosomal escape activities of a small molecule and cell penetrating peptides. ACS Chem. Biol. 14, 2641–2651 (2019).

A. Erazo-Oliveras, K. Najjar, D. Truong, T. Y. Wang, D. J. Brock, A. R. Prater, J. P. Pellois, The late endosome and its anionic lipid BMP act as gateways for the efficient cytosolic access of the cell-penetrating peptide dfTAT. Cell Chem. Biol. 23, 598–607 (2016).

Cellular delivery applications

Using our delivery techniques, we probe how proteins function inside cells. Recently, we successfully delivered proteins labeled with post-translational modifications (PTMs) or affinity probes (APs). For the former, this approach allows us to investigate how specific PTMs regulate what proteins do and where they go in a cell. In the latter, we are able to discover what proteins bind to in the context of a complex cellular environment. Simply put, we seek move classical biochemistry out of the test tube and into the cell.

Cell-to-cell communication

Human cells naturally communicate with one another by exchanging small vesicles called exosomes. We aim to understand how this membrane-exchange process works. To this end, we are developing probes that allow us to follow the step-by-step transport of membrane components between two cells. We are also developing new spectroscopic tools that can detect the surface composition and properties of exosomes at a single vesicle level. These tools are then used to establish how various populations of exosomes produce different cellular responses.