Project Summary / Abstract
Collagen lays the foundation of bodily tissues, serving to strengthen, connect, and signal from the micro to the
macro scale. The importance of collagen in cancer biology has been well-established: its functions in regulation
of the tumor microenvironment—from increased stiffness of the extracellular matrix to dysregulation of cancer
cell signaling—influence tumor proliferation and impenetrability. Key to these effects is the interaction between
fibrillar collagens and the discoidin domain receptor type 2 (DDR2), a receptor tyrosine kinase implicated in
multiple human cancers. Extracellular binding of fibrillar collagen to DDR2 transduces a cell signal that activates
epithelial to mesenchymal transition, proliferation, and metastasis. This work seeks to develop synthetic collagen
mimetic peptides (CMPs) for interrogation of the collagen-DDR2 interaction. As a permutated, triple helical
polymer involved in biochemical signaling, collagen has potential for manipulation as a tool for modulating
protein-protein interactions. These applications have been limited by its tripartite nature, which restricts its
thermal and entropic stability. Synthetic linkage and cyclization of the three collagen strands may overcome
these limitations. To this end, this work focuses on the design, synthesis, biophysical/structural characterization,
and biological application of linked and cyclic CMPs targeted against DDR2 through a chemical biology approach
described within two Aims. Aim 1 will evaluate the impact of strategic design strategies on the thermal and
proteolytic stability of the proposed CMPs, with a goal of maximizing stability. Aim 2 will investigate the ability of
the CMPs to interact with DDR2 in vitro and modulate DDR2 signaling in cellulo. Prior work has established a
method for synthesis of macrocyclic CMPs by solid phase peptide synthesis with on-resin cyclization, and
demonstrated that photoreaction of CMPs using diazirine-based photocrosslinking reagents can be used to
prepare unimolecular collagen heterotrimers. Several linked/cyclic as well as linear DDR2-targeted CMPs have
already been synthesized and have demonstrated appropriate thermal stability as well as capacity to interact
with DDR2. Methods include organic synthesis, photoreaction, circular dichroism, collagenase assay, isothermal
calorimetry, X-ray crystallography, and mammalian cell work coupled with Western blot. This work endeavors to
develop biochemical tools for modulation of the collagen interactome—concentrating on the cancer-implicated
interaction between collagen and DDR2—via an innovative chemical biology approach, laying the foundation for
new discoveries surrounding the role of collagen in cancer biology with potential for applications in drug
discovery. The robust, collaborative training environment at the University of Pennsylvania’s Department of
Chemistry and Perelman School of Medicine’s Medical Scientist Training Program—as well as a skilled
sponsorship team with expertise in organic synthesis, collagen structure and function, receptor tyrosine kinases,
crystallography, and cell biology—will support completion of the proposed fellowship work and facilitate the
rigorous training of an independent physician-scientist investigator.