PLD1 and ERK2 regulate cytosolic lipid droplet formation

Abstract

We have previously uncovered roles for phospholipase D (PLD) and an unknown cytosolic protein in the formation of cytosolic lipid droplets using a cell-free system. In this report, PLD1 has been identified as the relevant isoform, and extracellular signal-regulated kinase 2 (ERK2) as the cytosolic protein. Increased expression of PLD1 increased lipid droplet formation whereas knockdown of PLD1 using siRNA was inhibitory. A role for ERK2 in basal lipid droplet formation was revealed by overexpression or microinjection, and ablation by siRNA knockdown or pharmacological inhibition. Similar manipulations of other Map kinases such as ERK1, JNK1 or JNK2 and p38α or p38β were without effect. Insulin stimulated the formation of lipid droplets and this stimulation was inhibited by knockdown of PLD1 (by siRNA) and by inhibition or knockdown (by siRNA) of ERK2. Inhibition of ERK2 eliminated the effect of PLD1 on lipid droplet formation without affecting PLD1 activity, suggesting that PLD1 functions upstream of ERK2. ERK2 increased the phosphorylation of dynein which increased the amount of the protein on ADRP-containing lipid droplets. Microinjection of antibodies to dynein strongly inhibited the formation of lipid droplets, demonstrating that dynein has a central role in this formation. Thus dynein is a possible target for ERK2.

Monocyte Chemoattractant Protein-1/CC Chemokine Ligand 2 Controls Microtubule-Driven Biogenesis and Leukotriene B4-Synthesizing Function of Macrophage Lipid Bodies Elicited by Innate Immune Response

“…Our findings indicate that CCR2-driven lipid body biogenesis triggered by MCP-1 is dependent on downstream activation of PI3K and ERK1/2 kinases. Accordingly, activation of ERK 1/2 and PI3K in response to CC chemokines has been shown to participate in the regulated activation of lipid body biogenesis in other cell systems (25,32), as well as in other MCP-1-induced leukocyte functions (26,33). The specific isoform(s) involved in MCP-1-induced lipid body biogenesis are presently unknown.…”

“…Recent studies using NIH 3T3 cells stimulated with insulin have established that dynein, a microtubule motor, has a central role in the growth of lipid bodies by fusing them (36). Dynein required phosphorylation, performed by the MAPK ERK2, to interact with its cargos, such as lipid bodies and may potentially control lipid body assembly by providing the structural conditions required to let the lipid body arise from the ER membrane (32). In agreement with this hypothesis, here we showed that lipid body assembly triggered by activation of CCR2 by MCP-1 depends on activities of both ERK 1/2 kinases and the microtubular system of macrophages.…”

Increased lipolysis and altered lipid homeostasis protect γ-synuclein–null mutant mice from diet-induced obesity

“…In neuronal synapses, α-synuclein is involved in regulation of synaptic vesicle fusion with the cell membrane by promoting the assembly of SNARE complexes (11). In adipocytes, SNARE complexes have been implicated in lipid droplet formation and growth by fusion between neutral TAG packaged within amphipathic lipoproteins and the lipid droplet phospholipid monolayer (12)(13)(14)(15). To determine whether γ-synuclein may regulate the efficiency of this fusion mechanism, we quantified the assembled SNARE complexes in epididymal WAT lysates by measuring the amount of VAMP-4 (vSNARE) that coimmunoprecipitated with syntaxin-5 (tSNARE).…”

Morphology and histochemistry of glandular trichomes in Hyptis villosa Pohl ex Benth. (Lamiaceae) and differential labeling of cytoskeletal elements

“…The involvement of microtubules in the transport of oil drops is well established in animal cells (Zehmer et al 2009 and references therein). It has been showed that the ability of oil drops to form and grow in size (Andersson et al 2006) and their rapid movement in the cytoplasm (Gross et al 2000) is dependent on microtubules. So, we suggest that the more intense marking for microtubules in cells secreting abundant lipophilic compounds in H. villosa may be associated with the involvement of these elements in the intracellular transport of oil bodies.…”