Differentiation of Plasma Membrane Composition and Physical Properties

Abstract

Membrane organization into functional domains is a key feature of cell physiology. These domains spatially organize membrane components to actively regulate signal transduction across the membrane. Despite this broad biological impact, the lipid repertoires of different cell types, and their resulting regulation of plasma membrane (PM) organization and function remain to be determined. Mesenchymal stem cells (MSCs) are an ideal model system to investigate these questions, as they can differentiate into several functionally distinct lineages - here adipocytes and osteoblasts. We used MSCs to evaluate the differentiation of the PM phenotype, defined by (1) the detailed, comprehensive lipid composition; (2) biophysical properties, including liquid-liquid phase separation; and (3) functional signal transduction. We observed dramatic divergence of all three aspects of the PM phenotype during MSC differentiation. Using quantitative shotgun mass spectrometry, we found that adipocyte lipids have shorter and more saturated fatty acyl chains than undifferentiated cells, while osteogenic cell lipids have longer tails and are more polyunsaturated. These lipidomic rearrangements determined the physical properties of the PMs, with a divergence of both membrane fluidity and phase separation temperature during MSC differentiation. These observations elucidate the compositional determinants of biophysical properties in biological membranes, as well as identifying lineage-specific PM features. The unique membrane features of each cell type enabled rational remodeling of membrane phenotypes to direct differentiation. Supplementation with a lipid component overexpressed in osteoblasts (ꙍ-3 docosahexaneoic acid (DHA)) promoted an osteoblastic PM phenotype, and potentiated osteogenesis via alteration of signaling through the TGFβ pathway. These results comprise the first observations of compositional and biophysical differentiation of PMs, identify the compositional determinants of biological membranes physical properties, demonstrate the plasticity of cellular lipidomes, and enable rational engineering of the PM phenotype to promote desired cellular outcomes.