UC Berkeley

Living cells sense and respond to the biophysical cues of extracellular matrix (ECM) in a complex and reciprocal manner. Towards a comprehensive understanding of the regulatory roles of matrix biophysical properties, there is an emerging need for high-throughput matrix platforms that enable parallel culture of cells in various matrix conditions, and for systems biology approaches that can investigate cell-ECM interactions in a parallelized fashion. We provide an overview of recent progress in developing synthetic biomaterial platforms to probe cell-ECM interactions in a high-throughput manner and to profile such interactions at the systems level. We then describe a multi-well hyaluronic acid (HA) array platform in which cells are cultured on combinatorial arrays of gels spanning a range of elasticities and adhesivities. We validated the platform by recapitulating expected relationships between matrix stiffness, adhesivity and cell mechanosensing in human mesenchymal stem cells (hMSCs). We also showed that on this platform, hMSCs maintain the capability of adipogenesis and osteogenesis, and inguinal white adipose tissue (WAT) cells were capable of developing into beige adipocytes. This hydrogel array platform provides a versatile tool for dissecting molecular mechanisms of cell-ECM interactions.

Intrinsically disordered proteins (IDPs) play central roles in numerous cellular processes. While the structure and function of many IDPs are regulated by multisite phosphorylation, biophysical insights into the relationship between the modifications and structure are limited. The challenge calls for paradigms in which IDP conformational responses can be measured in the context of controlled phosphorylation. By engineering the disordered neurofilament heavy subunit sidearm domain (NFH-SA), we established recombinant NFH-SA (rNFH-SA) brushes on glass that can be controllably phosphorylated in situ with pre-activated mitogen-activated protein kinase 1, and monitored brush conformations with atomic force microscopy. Phosphorylation induced significant brush swelling to an extent that strongly depends upon pH and ionic strength. The phosphorylated rNFH-SA brush was also dramatically condensed with micromolar concentrations of divalent cations. Our study demonstrates that multisite phosphorylation controls NFH-SA structure through modulation of chain electrostatics and points to a general strategy for engineering IDP-based interfaces that can be reversibly and dynamically modulated by enzymes.