Sterols lower energetic barriers of membrane bending and fission necessary for efficient clathrin mediated endocytosis

Abstract

SUMMARYAs the principal internalization mechanism in mammalian cells, clathrin-mediated endocytosis (CME) is critical for cellular signal transduction, receptor recycling, and membrane homeostasis. Acute depletion of cholesterol disrupts CME, motivating analysis of CME dynamics in the context of disrupted cholesterol synthesis, sterol specificity, mechanisms involved, and relevance to disease pathology. Using genome-edited cell lines, we demonstrate that inhibition of post-squalene cholesterol biosynthesis as observed in inborn errors of cholesterol metabolism, results in striking immobilization of CME and impaired transferrin uptake. Imaging of membrane bending dynamics and CME pit ultrastructure revealed prolonged clathrin pit lifetimes and accumulation of shallow clathrin-coated structures that scaled with diminishing sterol abundance. Moreover, fibroblasts derived from Smith-Lemli-Opitz syndrome subjects displayed reduced CME function. We conclude that sterols lower the energetic costs of membrane bending during pit formation and vesicular scission during CME and suggest reduced CME contributes to cellular phenotypes observed within disorders of cholesterol metabolism.

Endosomal Cholesterol in Viral Infections – A Common Denominator?

“…Both clustering and activity hereof is enhanced by cholesterol ( Lang et al, 2001 ; Milovanovic et al, 2015 ; Stratton et al, 2016 ), which renders the lipid being intertwined with the fate of vesicular fusion. On the other hand, endosomal cholesterol also regulates and is regulated by dynamin-mediated vesicle fission ( Robinet et al, 2006 ; Anderson et al, 2021 ) and is required for ESCRT-mediated ILV scission ( Kobayashi et al, 2002 ; Boura et al, 2012 ; Bissig and Gruenberg, 2013 ). This strict regulation of membrane fusion and fission by cholesterol is accompanied by directed trafficking of endosomes along microtubules in the process of their maturation.…”

Effect of Hypoxia on the Function of the Human Serotonin1A Receptor

“…57,58 In order to avoid the uptake of exogenous cholesterol from the serum present in a complete culture medium, we cultured cells in a serum-free medium under hypoxic conditions. 59 To rule out any possible effect of the serum-free medium itself, control cells were grown in both complete and serum-free culture media under normoxic conditions for 24 h (see Figures 2 and S1).…”