Cytoskeletal association of ATP citrate lyase controls the mechanodynamics of macropinocytosis

Abstract

Macropinocytosis is an actin-dependent mode of non-selective endocytosis that mediates the uptake of extracellular fluid-phase cargoes. It is now well-recognized that tumor cells exploit macropinocytosis to internalize macromolecules that can be catabolized and used to support cell growth and proliferation under nutrient limiting conditions. Therefore, the identification of molecular mechanisms that control macropinocytosis is fundamental to the understanding of the metabolic adaptive landscape of tumor cells. Here we report that the acetyl-CoA producing enzyme, ATP citrate lyase (ACLY), is a key regulator of macropinocytosis and describe a heretofore unappreciated association of ACLY with the actin cytoskeleton. The cytoskeletal tethering of ACLY is required for the spatially-defined acetylation of heterodimeric actin capping protein, which we identify as an essential mediator of the actin remodeling events that drive membrane ruffling and macropinocytosis. Furthermore, we identify a requirement for mitochondrial-derived citrate, an ACLY substrate, for macropinocytosis, and show that mitochondria traffic to cell periphery regions juxtaposed to plasma membrane ruffles. Collectively these findings establish a new mode of metabolite compartmentalization that supports the spatiotemporal modulation of membrane-cytoskeletal interactions required for macropinocytosis by coupling regional acetyl-CoA availability with dynamic protein acetylation. SignificanceThe scavenging of extracellular macromolecules via macropinocytosis is a key adaptive mechanism that supports the metabolic fitness of cancer cells. Although the importance of macropinocytosis for sustaining tumor cell growth under nutrient limiting conditions is well documented, less is known about the molecular mechanisms by which macropinocytosis is regulated. This study describes a previously uncharacterized dependence of macropinocytosis on the compartmentalized generation of acetyl-CoA through the association of ACLY with the actin cytoskeleton. This metabolic channeling process establishes a new mechanistic framework for understanding actin remodeling events that drive macropinocytosis.