Mammalian lipins (lipin-1, lipin-2, and lipin-3) are Mg 2؉ -dependent phosphatidate phosphatase (PAP) enzymes, which catalyze a key reaction in glycerolipid biosynthesis. Lipin-1 also functions as a transcriptional coactivator in conjunction with members of the peroxisome proliferator-activated receptor family. An S734L mutation in LPIN2 causes Majeed syndrome, a human inflammatory disorder characterized by recurrent osteomyelitis, fever, dyserythropoietic anemia, and cutaneous inflammation. Here we demonstrate that mutation of the equivalent serine in mouse lipin-1 and lipin-2 to leucine or aspartate abolishes PAP activity but does not impair lipin association with microsomal membranes, the major site of glycerolipid synthesis. We also determined that lipin-2 has transcriptional coactivator activity for peroxisome proliferator-activated receptor-response elements similar to lipin-1 and that this activity is not affected by mutating the conserved serine. Therefore, our results indicate that the symptoms of the Majeed syndrome result from a loss of lipin-2 PAP activity. To characterize sites of lipin-2 action, we detected lipin-2 expression by in situ hybridization on whole mouse sections and by quantitative PCR of tissues relevant to Majeed syndrome. Lipin-2 was most prominently expressed in liver, where levels were much higher than lipin-1, and also in kidney, lung, gastrointestinal tract, and specific regions of the brain. Lipin-2 was also expressed in circulating red blood cells and sites of lymphopoiesis (bone marrow, thymus, and spleen). These results raise the possibility that the loss of lipin-2 PAP activity in erythrocytes and lymphocytes may contribute to the anemia and inflammation phenotypes observed in Majeed syndrome patients.The mammalian lipin protein family is composed of three members, lipin-1, lipin-2, and lipin-3, each of which are ϳ100 kDa in size and have 44 -48% amino acid similarity (reviewed in Ref. 1). Orthologous lipin genes are present in plants, invertebrates, and single cell eukaryotes such as yeast and plasmodium (2), suggesting that lipin proteins play a fundamental cellular role that has been conserved in evolution. In particular, extended stretches of 100 -200 amino acids at the N-terminal and C-terminal regions of the protein (the N-LIP and C-LIP domains, respectively) are highly conserved among the three mammalian lipin family members and among species. Within the C-LIP domain are two key protein functional motifs as follows: a haloacid dehalogenase motif (DXDXT) found in a superfamily of Mg 2ϩ -dependent phosphatases (3, 4), and a transcription factor-binding motif (LXXIL) (5). These motifs confer two distinct molecular functions on members of the lipin family. All three mammalian lipins are Mg 2ϩ -dependent phosphatidate phosphatase (PAP) 4 enzymes, which catalyze the conversion of phosphatidate (PA) to diacylglycerol, a key step in the biosynthesis of triacylglycerol, phosphatidylcholine, and phosphatidylethanolamine (3, 4, 6, 7). Lipin-1 also acts as a transcriptional coact...
Lipin-1 deficiency in the mouse causes generalized lipodystrophy, characterized by impaired adipose tissue development and insulin resistance. Lipin-1 expression in differentiating preadipocytes is required for normal expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor g and CCAAT enhancer binding protein a, and for the synthesis of triacylglycerol. The requirement of lipin-1 for adipocyte differentiation can be explained, in part, by its activity as the sole adipocyte phosphatidic acid phosphatase-1 enzyme, which converts phosphatidate to diacylglycerol, the immediate precursor of triacylglycerol. Here we identify glucocorticoids as the stimulus for the induction of lipin-1 expression in differentiating adipocytes, and characterize a glucocorticoid response element (GRE) in the Lpin1 promoter. The Lpin1 GRE binds to the glucocorticoid receptor and leads to transcriptional activation in adipocytes and hepatocytes, as demonstrated by reporter gene transcription, electrophoretic mobility shift, and chromatin immunoprecipitation assays. This represents the first gene regulatory element identified to directly influence lipin-1 expression levels, and may modulate lipin-1 mRNA levels in adipose tissue and liver in conditions associated with increased local glucocorticoid concentrations in vivo, such as obesity and fasting.-Zhang, P., L. OʼLoughlin, D. N. Brindley, and K. Reue. Regulation of lipin-1 gene expression by glucocorticoids during adipogenesis. J. Lipid Res. 2008Res. . 49: 1519Res. -1528
SARS-CoV-2 infection in children produces mild respiratory symptoms or no symptoms at all in most cases. Some pediatric patients develop a severe complication associated with high mortality, the multisystem inflammatory syndrome in children (MIS-C). In both scenarios, there are reports of neurological manifestations. This article aims to review the cases of pediatric patients with severe neurological issues and a coexisting positive SARS-CoV-2 test. A literature search was performed between March 2020 and May 2021. The results included the data from 41 studies, with 159 children with severe neurological manifestations, within an age range from 24 h to 17 years. The neurological disorders included 38 cases with stroke, 32 with encephalitis, 22 with encephalopathy, and 10 with Guillain–Barre syndrome. Sixty-five out of 159 cases with severe neurological manifestations were diagnosed with MIS-C. Direct neuroinvasion and the exaggerated immune response in some patients seem to be the most critical factors triggering these manifestations. Further research in the ongoing pandemic is needed to elucidate the precise mechanism.
Cerebrofacial arteriovenous metameric syndrome (CAMS) is a recent classification of vascular malformations that encompasses a spectrum of phenotypic expression involving arteriovenous malformations (AVMs) of the cerebral, orbital, and facial region. Recognizing the embryologic basis of CAMS is important for diagnosing other AVMs along the same metameric level. Visual loss is the most common presentation prompting ophthalmologic evaluation followed by neuroimaging. We present two pediatric patients with ipsilateral optic nerve and chiasmal AVMs without cutaneous manifestations, characteristic of CAMS 2. The diagnosis of cerebral AVMs was made by magnetic resonance imaging of the brain and confirmed with cerebral angiography. High-resolution flat-panel computed tomography was performed in one patient and was useful to demonstrate the intraneural invasion of the optic nerve by the AVM.
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