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Role for formin-like 1-dependent acto-myosin assembly in lipid droplet dynamics and lipid storage.

Nature communications (2017-04-01)
Simon G Pfisterer, Gergana Gateva, Peter Horvath, Juho Pirhonen, Veijo T Salo, Leena Karhinen, Markku Varjosalo, Samppa J Ryhänen, Pekka Lappalainen, Elina Ikonen
ABSTRACT

Lipid droplets (LDs) are cellular organelles specialized in triacylglycerol (TG) storage undergoing homotypic clustering and fusion. In non-adipocytic cells with numerous LDs this is balanced by poorly understood droplet dissociation mechanisms. We identify non-muscle myosin IIa (NMIIa/MYH-9) and formin-like 1 (FMNL1) in the LD proteome. NMIIa and actin filaments concentrate around LDs, and form transient foci between dissociating LDs. NMIIa depletion results in decreased LD dissociations, enlarged LDs, decreased hydrolysis and increased storage of TGs. FMNL1 is required for actin assembly on LDs in vitro and for NMIIa recruitment to LDs in cells. We propose a novel acto-myosin structure regulating lipid storage: FMNL1-dependent assembly of myosin II-functionalized actin filaments on LDs facilitates their dissociation, thereby affecting LD surface-to-volume ratio and enzyme accessibility to TGs. In neutrophilic leucocytes from MYH9-related disease patients NMIIa inclusions are accompanied by increased lipid storage in droplets, suggesting that NMIIa dysfunction may contribute to lipid imbalance in man.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Monoclonal Anti-α-Tubulin antibody produced in mouse, clone B-5-1-2, purified immunoglobulin, buffered aqueous solution
Sigma-Aldrich
DL-Cysteine, technical grade
Sigma-Aldrich
Monoclonal Anti-Myosin (Light Chains 20 kDa) antibody produced in mouse, clone MY-21, ascites fluid
Sigma-Aldrich
Anti-FMNL1 antibody produced in rabbit, Prestige Antibodies® Powered by Atlas Antibodies, affinity isolated antibody, buffered aqueous glycerol solution