Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

53-POS Board 14 THE DESMOGLEIN TRANSMEMBRANE DOMAIN DETERMINES ASSOCIATION WITH ORDERED LIPID DOMAINS TO ASSEMBLE ROBUST DESMOSOMES Stephanie E Zimmer 1 ; Mateusz Sikora 3 ; Ilya Levental 4 ; Andrew P Kowalczyk 1,2 ; 1 Penn State College of Medicine, Dermatology, Hershey, PA, USA 2 Penn State College of Medicine, Cellular and Molecular Physiology, Hershey, PA, USA 3 Max Planck Institute of Biophysics, Frankfurt, Germany 4 University of Virginia, Molecular Physiology and Biological Physics, Charlottesville, VA, USA Cholesterol- and sphingolipid-enriched ordered lipid domains, or “lipid rafts,” selectively recruit proteins for specific functions. However, mechanisms driving certain membrane proteins into such domains while excluding others are not fully understood. Intercellular adhesive junctions called desmosomes are ordered mesoscale lipid domains that represent unique models for understanding these mechanisms. Desmosomes confer robust mechanical strength to tissues by linking intermediate filament networks of adjacent cells through a series of adaptor proteins assembled at cell borders by adhesive desmogleins (DSG) and desmocollins. A unique disease- causing mutation resulting in a glycine to arginine substitution in the DSG1 transmembrane domain (TMD) abrogates association with ordered lipid domains to disrupt desmosome assembly and adhesive function, suggesting that the DSG TMD supports these processes through partitioning to ordered lipid environments. TMD physical properties, including length, exposed surface area, and palmitoylation, have been shown to drive raft association of single-pass transmembrane proteins like DSG. We hypothesized that TMD physical properties drive DSG raft association to promote desmosome assembly and function. We created a panel of GFP- tagged DSG1 TMD variants by individually modifying each of the above properties and stably expressed these DSG1 TMD -GFP variants in DSG-null cells. Sucrose gradient fractionations showed reduced raft partitioning for variants with altered TMD length or exposed surface area while loss of palmitoylation had no effect. Super-resolution imaging and functional assays revealed a linear relationship between DSG1 TMD lipid raft association and the assembly of morphologically and functionally robust desmosomes. These findings suggest that DSG raft association is an important nucleation step during desmosome assembly and that strong desmosome adhesion requires raft association. We propose that reduced association with ordered lipid domains is an underlying disease mechanism in some inherited human diseases.

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