CGI-58/ABHD5 is a coenzyme A-dependent lysophosphatidic acid acyltransferase.

Mutations in human CGI-58/ABHD5 cause Chanarin-Dorfman syndrome (CDS), characterized by excessive storage of triacylglycerol in tissues. CGI-58 is an alpha/beta-hydrolase fold enzyme expressed in all vertebrates. The carboxyl terminus includes a highly conserved consensus sequence (HXXXXD) for acyltransferase activity. Mouse CGI-58 was expressed in Escherichia coli as a fusion protein with two amino terminal 6-histidine tags. Recombinant CGI-58 displayed acyl-CoA-dependent acyltransferase activity to lysophosphatidic acid, but not to other lysophospholipid or neutral glycerolipid acceptors. Production of phosphatidic acid increased with time and increasing concentrations of recombinant CGI-58 and was optimal between pH 7.0 and 8.5. The enzyme showed saturation kinetics with respect to 1-oleoyl-lysophosphatidic acid and oleoyl-CoA and preference for arachidonoyl-CoA and oleoyl-CoA. The enzyme showed slight preference for 1-oleoyl lysophosphatidic acid over 1-palmitoyl, 1-stearoyl, or 1-arachidonoyl lysophosphatidic acid. Recombinant CGI-58 showed intrinsic fluorescence for tryptophan that was quenched by the addition of 1-oleoyl-lysophosphatidic acid, oleoyl-CoA, arachidonoyl-CoA, and palmitoyl-CoA, but not by lysophosphatidyl choline. Expression of CGI-58 in fibroblasts from humans with CDS increased the incorporation of radiolabeled fatty acids released from the lipolysis of stored triacylglycerols into phospholipids. CGI-58 is a CoA-dependent lysophosphatidic acid acyltransferase that channels fatty acids released from the hydrolysis of stored triacylglycerols into phospholipids.

The association between neuroblastoma and opsoclonus-myoclonus syndrome: a historical review.

An association between neuroblastoma and opsoclonus-myoclonus syndrome (OMS) was described as early as 1927 within the first report on the transformation of malignant neuroblastoma to a benign ganglioneuroma. It was not recognized at that time nor was it appreciated in the subsequent follow-up report on the same patient in 1959. Myoclonic encephalopathy of infancy, an alternative name for OMS, was described by a pediatric neurologist in 1962; however, its connection to neuroblastoma was not known. It was only in 1968 that the association between these two conditions was first reported. The neuroblastoma tumors associated with OMS are almost all small, stage I-II with no associated MYCN amplification or metastases. OMS occurs in 2-3% of patients with neuroblastoma, but neuroblastoma is found in as many as 50% of children who present with OMS. Nearly 100% of the children with neuroblastoma associated with OMS survive, and this has led to speculation that the OMS is a result of an autoimmune process, not metastases. Affected children are treated with steroids, ACTH, or intravenous immunoglobulin, but many have persistent neurologic and developmental deficits. Using the original case reported in 1927, we summarize a century of literature in this review on OMS and its association with neuroblastoma.

Perilipin A and the control of triacylglycerol metabolism.

Perilipin A is the most abundant protein associated with the lipid droplets of adipocytes and functions to control both basal and stimulated lipolysis. Under basal or fed conditions, perilipin A shields stored triacylglycerols from cytosolic lipases, thus promoting triacylglycerol storage. When catecholamines bind to cell surface receptors to initiate signals that activate cAMP-dependent protein kinase (PKA), phosphorylated perilipin A facilitates maximal lipolysis. Mutagenesis studies have revealed that central sequences of moderately hydrophobic amino acids are required to target nascent perilipin A to lipid droplets and provide an anchor into the hydrophobic environment of lipid droplets. Sequences of amino acids in the unique carboxyl terminus of perilipin A and those in amino terminal sequences flanking the first hydrophobic stretch are required for the barrier function of perilipin A in promoting triacylglycerol storage. Site-directed mutagenesis studies of serine residues within six PKA consensus sites of perilipin A reveal functions for phosphorylation of at least three of the sites. Phosphorylation of one or more of the serines within three amino terminal PKA sites is required to facilitate hormone-sensitive lipase access to lipid substrates. Phosphorylation of serines within two carboxyl terminal sites is also required for maximal lipolysis. Phosphorylation of serine 492 (site 5) triggers a massive remodeling of lipid droplets, whereby large peri-nuclear lipid droplets fragment into myriad lipid micro-droplets that scatter throughout the cytoplasm. We hypothesize that perilipin A binds accessory proteins to provide assistance in carrying out these functions.

Neuroblastoma-remembering the three physicians who described it a century ago: James Homer Wright, William Pepper, and Robert Hutchison.

Neuroblastoma is often widespread at the time of diagnosis. Three physicians between 1900 and 1910 played an important role in the pathologic definition of neuroblastoma and its route of spread in relation to the age of the patient. These findings eventually led to the advances in treatment and decreased morbidity of today. In 1910 James Homer Wright was the first to recognize the tumor as being of primitive neural cell origin, calling it neuroblastoma and emphasizing the bundle of cells termed rosettes. While Wright recognized the neural nature of the tumor, the authors of previous reports had described its two distinct patterns of spread. In 1901 William Pepper published a series of infants with massive hepatic infiltration associated with adrenal tumors without spread to bone, and in 1907 Robert Grieve Hutchison reported his experience with a similar pathologic process in older infants and children who had orbital and skull metastases. Wright's valuable unifying concept served to tie together the descriptions of Pepper and Hutchison. A century later the names of these physicians should be remembered-Wright, who defined the adrenal tumor as of primitive neural origin, Pepper for his clinically accurate report of massive liver involvement in the infant, and Hutchison for describing the propensity of the tumor to spread to bone in older children.

Hypervitaminosis A-induced premature closure of epiphyses (physeal obliteration) in humans and calves (hyena disease): a historical review of the human and veterinary literature.

Vitamin A toxicity in the infant, which now occurs rarely from dietary overdosage, was recognized in the 1940s as painful periostitis with rare progression to premature closure of the lower limb epiphyses. Decades later, most cases of vitamin A-induced premature epiphyseal closure (physeal obliteration) occur in pediatric dermatologic patients given vitamin A analogues. This phenomenon resembles a strange disease discovered in more recent years in calves with closed epiphyses of the hind limbs, known as hyena disease. This was a mystery until proved to be caused by vitamin A toxicity from enriched grain that causes the calves to have short hind limbs that resemble those of a hyena and gait disturbance. This historical review links the human and veterinary literature in terms of vitamin A-induced epiphyseal closure using a case report format of a 16-month-old human infant with closed knee epiphyses and gait disturbance that is reminiscent of hyena disease seen in calves.

Perilipin A mediates the reversible binding of CGI-58 to lipid droplets in 3T3-L1 adipocytes.

Perilipins, the major structural proteins coating the surfaces of mature lipid droplets of adipocytes, play an important role in the regulation of triacylglycerol storage and hydrolysis. We have used proteomic analysis to identify CGI-58, a member of the alpha/beta-hydrolase fold family of enzymes, as a component of lipid droplets of 3T3-L1 adipocytes. CGI-58 mRNA is highly expressed in adipose tissue and testes, tissues that also express perilipins, and at lower levels in liver, skin, kidney, and heart. Both endogenous CGI-58 and an ectopic CGI-58-GFP chimera show diffuse cytoplasmic localization in 3T3-L1 preadipocytes, but localize almost exclusively to the surfaces of lipid droplets in differentiated 3T3-L1 adipocytes. The localization of endogenous CGI-58 was investigated in 3T3-L1 cells stably expressing mutated forms of perilipin using microscopy. CGI-58 binds to lipid droplets coated with perilipin A or mutated forms of perilipin with an intact C-terminal sequence from amino acid 382 to 429, but not to lipid droplets coated with perilipin B or mutated perilipin A lacking this sequence. Immunoprecipitation studies confirmed these findings, but also showed co-precipitation of perilipin B and CGI-58. Remarkably, activation of cAMP-dependent protein kinase by the incubation of 3T3-L1 adipocytes with isoproterenol and isobutylmethylxanthine disperses CGI-58 from the surfaces of lipid droplets to a cytoplasmic distribution. This shift in subcellular localization can be reversed by the addition of propanolol to the culture medium. Thus, CGI-58 binds to perilipin A-coated lipid droplets in a manner that is dependent upon the metabolic status of the adipocyte and the activity of cAMP-dependent protein kinase.