The phosphorylation of serine 492 of perilipin A directs lipid droplet fragmentation and dispersion

Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA.
Journal of Biological Chemistry (Impact Factor: 4.6). 05/2006; 281(17):11901-9. DOI: 10.1074/jbc.M600171200
Source: PubMed

ABSTRACT Perilipin A is a key regulator of triacylglycerol storage and hydrolysis in adipocytes; phosphorylation of perilipin A by protein kinase A facilitates maximal lipolysis. Chronic stimulation of lipolysis in 3T3-L1 adipocytes causes large perinuclear lipid droplets to fragment into myriad dispersed perilipin A-covered microlipid droplets. In cultured fibroblasts stably expressing ectopic perilipin A, clustered lipid droplets disperse throughout the cytoplasm upon incubation of the cells with forskolin and isobutylmethylxanthine (IBMX) to elevate levels of cAMP and activate protein kinase A, mirroring events observed in adipocytes. Furthermore, diethylum-belliferyl phosphate inhibits stimulated lipolysis but not the dispersion of lipid droplets, suggesting that products of lipolysis are not required for this remodeling process. We hypothesized that protein kinase A-mediated phosphorylation of perilipin A triggers the remodeling of lipid droplets. The mutation of serine 492 of perilipin A to alanine prevented the dispersion of clustered lipid droplets in fibroblasts stably expressing the mutated perilipin upon incubation with forskolin and IBMX. In contrast, the substitution of serines 81, 222, 276, or 433 with alanine, either singly or in combinations, did not affect the protein kinase A-mediated remodeling of lipid droplets. Interestingly, substitution of serines 433, 492, and 517 of perilipin A with glutamic acid residues blocked the dispersion of clustered lipid droplets in cells incubated with forskolin and IBMX, indicating that the addition of a negative charge does not mimic a phosphate group. We conclude that protein kinase A-mediated phosphorylation of serine 492 of perilipin A drives the fragmentation and dispersion of lipid droplets.

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    • "Interestingly, LD clustering has also been observed in other cellular models, without HCV infection. In some cases, the degree of LD clustering seemed to depend on the metabolic state, with lipolysis counteracting clustering (Marcinkiewicz et al., inserm-00664942, version 1 -31 Jan 2012 2006). In the yeast model, the absence of seipin, a LD-associated protein, resulted in a LD "
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    Biology of the Cell 05/2011; 103(5):223-31. DOI:10.1042/BC20100119 · 3.87 Impact Factor
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    • "Perilipin is detected at 62 kDa. A polyclonal antibody against Phospho-(Ser/Thr) PKA Substrate (Cell Signaling Technology, USA; dilution 1:1000) was used for the detection of phosphorylated perilipin (Marcinkiewicz et al., 2006; Miyoshi et al., 2006). A protein of 67 kDa can be observed. "
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    • "PAT proteins may regulate lipolysis by modulating the LD surface structure and changing the accessibility of lipid esters to the lipases. Another phenomenon that is ascribed to perilipin A is the appearance of microsized LDs after lipolytic stimulation (Marcinkiewicz et al. 2006). Disruption of a sphere into many small spheres may be a mechanism to facilitate lipolysis by increasing the surface-to-volume ratio, but microsized LD formation has not been shown to correlate closely to release of lipolytic products (Bickel et al. 2009), and seem to be generated in a region distant from the original LD (Yamaguchi et al. 2007; Nagayama et al. 2010). "
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