Speakers
- Prof. Trevor GrandPre — Washington University in St. Louis
Abstract
Biomolecular condensates are commonly organized by scaffold molecules that drive phase separation and client molecules that do not condense independently but become selectively enriched within the dense phase. In addition, molecules within condensates are continually remodeled by biochemical reactions that can have history-dependent, non-Markovian dynamics. In this talk, I will seek to address how client enrichment feeds back on scaffold interactions to regulate condensate composition and phase behavior, how biochemical memory naturally arises in condensates, and how biochemical memory generically gives rise to self-propelled condensates. The talk will be divided into two parts, both motivated by the role of biomolecular condensates in focal adhesions: one regarding client enrichment and the other on biochemical memory. First, I will address the role of client enrichment in a reconstituted focal-adhesion system composed of focal adhesion kinase (FAK) and a phosphorylated p130Cas–Nck–N-WASP network (collectively, Cas) as scaffolds, with the adaptor protein paxillin (PXN) as a client. An associative-polymer model predicts both single- and multi-condensate regimes with distinct scaffold compositions, while experimentally constrained parameters favor a single FAK–Cas–PXN co-condensate biased toward FAK. In the biochemical memory section of my talk, I will describe a new model of active phase separation with non-Markovian reactions. I will show that delayed reaction feedback destabilizes stationary droplets: when the memory time becomes comparable to the reaction turnover time, condensates deform and spontaneously acquire a polar, self-propelled state. In multidroplet systems, persistent biochemical memory mediates alignment, producing polar flocks and, at higher concentrations, traveling labyrinths. These results reveal how client enrichment, post-translational modifications, and biochemical memory regulate condensate composition, phase behavior, and dynamics, giving rise to self-propulsion and collective organization.
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