Abstract: Cell remodeling relies on dynamic rearrangements of cell contacts powered by the actin cytoskeleton. The tumor suppressor Adenomatous Polyposis Coli (APC) nucleates actin filaments (F-actin) and localizes at cell junctions. Whether APC-driven actin nucleation acts in cell junction remodeling remains unknown. By combining bioimaging and genetic tools with artificial intelligence algorithms applied to colorectal cancer cell monolayers, we found that the APC-dependent actin pool contributes to sustaining levels of F-actin, as well as E-cadherin and Occludin protein levels at cell junctions. Moreover, this activity preserved cell junction length, angle, and motion, as well as vertex motion and integrity. Loss of this F-actin pool led to larger cells with slow and random cell movement within a sheet. Our findings suggest that APC-driven actin nucleation promotes cell junction integrity and dynamics to facilitate collective cell remodeling and consequent motility. Our study offers a new perspective to explore the relevance of APC-driven cytoskeletal function in gut morphogenesis.

Abstract: A key challenge for any medical field remains how to deliver drugs to the desired site of action to achieve optimal outcomes while minimizing unwanted side effects. The design of novel polypeptide-based drug carriers represents an opportunity to improve the treatment of diseases with unmet clinical needs (such as neurodegenerative diseases or cancer) by altering pharmacokinetics and pharmacological properties to improve patient outcomes. Specific alterations to the amino acids composition of polypeptides can improve diversity and generate materials with inherent therapeutic activities, which may trigger synergism with conjugated neurodegenerative disease-targeted drugs. For example, Copaxone®, a first-line treatment for multiple sclerosis, was developed with selected amino acids to act as a polymeric drug.

We have combined expertise in capturing the “ordinary-extraordinary” transition behavior of polypeptides with microfluidics to control synthesis and hence cut production costs, increase reproducibility, and increase conjugate homogeneity at large scales. To begin this process, we optimized microfluidic flow parameters to support the controlled synthesis of crosslinked, self-assembled star-shaped polypeptides through two different strategies: (i) biodegradable, using redox-responsive (disulfide) linkers (using the prior derivatization of unimers with pyridyl moieties), and (ii) non-biodegradable, involving tetrazine-based ligation based on inverse- and then retro-Diels-Alder reaction. Tetrazines react with strain alkenes; in our case, we selected norbornene as the ideal candidate. We fully characterized crosslinked, self-assembled star-shaped polypeptides and studied their stability under physiological conditions. We then used post-polymerization modifications with single agents and drug combinations to create crosslinked, self-assembled star-shaped polypeptide-based nanomedicines. We are currently exploring their full therapeutic potential in microglial cells in vitro.