(316f) Genetically Encoded, Synthetic Glycopolymers for Tunable Control of Plasma Membrane Shapes and Organelle Biogenesis

Highly curved, plasma-membrane organelles, such as microvilli, cilia, filapodia, axons, and cytonemes, are ubiquitous and essential in multicellular life. The understanding of the underlying mechanisms for formation of these essential organelles remains limited, as do modular strategies and tools for precision control over them. Here, we find that the plasma membrane bending is driven entropically by flexible glycoproteins and glycopolymers anchored to the plasma membrane. Based on these observations, we developed a library of natural, semi-synthetic, and fully synthetic cDNAs that encode glycoprotein products of varying configurational entropy for controlling membrane shapes. Specifically, we developed a modular library of repetitive mucin domains of varying length and extent of glycosylation, and fused these domains to membrane anchors for cell surface expression. The mucin-type proteins with their pendant O-glycans are structurally analogous to semi-flexible bottlebrush polymers. We show that our constructs can program membrane shapes from nearly flat to fully tubulated. Furthermore, we developed an entropic polymer brush model, which predicts the structure of the experimentally observed cell-membrane tubes and informs the design of additional glycoprotein modules. In addition to its application in synthetic biology, our work reveals a new potential function and mechanism by which flexible glycans and glycoproteins regulates cell membrane shape and organelle biogenesis.