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Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI family. We previously reported that LGI3 increased in obese adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a pro-inflammatory adipokine secreted predominantly by preadipocytes and macrophages. In this study, we showed that LGI3 and tumor necrosis factor-α (TNF-α) upregulated each other in 3T3-L1 cells. Treatment of 3T3-L1 preadipocytes with LGI3 protein increased TNF-α mRNA and protein. LGI3 treatment led to NF-κB activation and binding to an NF-κB binding site (-523 to -514) in TNF-α promoter. TNF-α treatment increased mRNA and protein expression of LGI3 and ADAM23. TNF-α increased NF-κB binding to a predicted binding site (-40 to -31) in LGI3 promoter. High fat diet-fed mice showed that LGI3 and TNF-α were increased and colocalized in adipose tissue inflammation. Taken together, these results suggested that mutual upregulation of LGI3 and TNF-α may play a role in adipose tissue inflammation in obesity., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Leucine‐rich repeat LGI family member 3 (LGI3), a member of the LGI family, is a secreted protein that is expressed not only in the brain and adipose tissues, but also in various skin cells. We previously reported that LGI3 was secreted after exposure to ultraviolet B and promoted the migration of HaCaT human keratinocytes. In the present study, we investigated whether LGI3 influences the differentiation of keratinocytes. The results show that the expression of involucrin, a keratinocyte differentiation marker, was reduced in tissue from LGI3‐knockout mice. Those results indicate that LGI3 plays an important role in keratinocyte differentiation. Therefore, we treated HaCaT cells with LGI3 to examine its effect on keratinocyte differentiation. Protein levels of various differentiation markers were enhanced by treatment with LGI3. Furthermore, expression of differentiation markers was inhibited when keratinocytes were transfected with an siRNA for LGI3. LGI3 strongly activated Akt, whereas it had no apparent effect on extracellular signal‐regulated kinase, p38 mitogen‐activated protein kinase, or the c‐Jun N‐terminal kinase. A specific inhibitor of phosphoinositide 3‐kinase, LY294002, reduced LGI3‐induced expression of differentiation markers in HaCaT cells. Taken together, these results suggest that LGI3 promotes keratinocyte differentiation and could be used as a therapeutic agent to recover skin barrier function in epidermal barrier disruption. [ABSTRACT FROM AUTHOR]

Leucine‑rich glioma inactivated 3 (LGI3) is a secreted protein in vertebrates, which belongs to the LGI family. In our previous study, LGI3 was found to be expressed in brain, adipose tissues and the skin, where it functions as a multifunctional cytokine. In the present study, we used bioinformatic tools to perform data mining, phylogenetics and prognostic association analysis to investigate the prognostic role of LGI3 in cancers. The sequences of LGI3 orthologues were analyzed from various species, and it was found that LGI3 was highly conserved in mammals and that the subsets of amino acid residues were phylogenetically coevolved in four major clusters. Single nucleotide polymorphisms (SNPs) of the human LGI3 gene included 228 functionally relevant variants (missense, nonsense and frameshift) in a total of 1,042 SNPs. Four missense SNPs had a global minor allele frequency ≥0.001. Somatic mutations in cancer with functional relevance were found in various types of cancer, including uterine, stomach and lung cancer. In addition, five amino acid residues with cancer mutations were shown to be coevolved in the vertebrate phylogeny, suggesting their importance in protein dysfunctions in cancer. One conserved amino acid and three SNPs were found to be mutated in stomach cancer and melanoma. Analysis of expression microarray data demonstrated that the expression of LGI3 was significantly associated with the prognosis of brain, colorectal and lung cancer. Taken together, these results suggested that the genetic variations and expression levels of LGI3 have potential value in cancer prognosis. [ABSTRACT FROM AUTHOR]

Highlights: [•] We found that adiponectin was increased in adipose tissues and plasma of LGI3 knockout mice. [•] LGI3 was upregulated whereas adiponectin was downregulated in high fat diet-fed obese mice. [•] Knockdown of LGI3 increased adiponectin and treatment with LGI3 protein decreased adiponectin in 3T3-L1 cells. [•] We propose that LGI3 may be a pro-inflammatory adipokine candidate that negatively regulates adiponectin. [ABSTRACT FROM AUTHOR]

Abstract: Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein and a member of LGI/epitempin family. We previously showed that LGI3 was highly expressed in brain and played regulatory roles in neuronal exocytosis and differentiation. Besides the nervous system, LGI3 was shown to be expressed in diverse tissues. In this study, we found that LGI3 and its receptor candidate ADAM23 were expressed in adipose tissues and 3T3-L1 cells. 3T3-L1 preadipocytes secreted a 60-kDa protein, a major secreted form of LGI3, which declined with adipocyte differentiation. LGI3 was also expressed in adipose tissue macrophages in the ob/ob mice and in macrophage cell line. The 60-kDa LGI3 protein was selectively increased in the ob/ob adipose tissues comparing with the lean mice. Pull-down experiments, coimmunoprecipitation and immunocytochemistry indicated that LGI3 associated with ADAM23 in adipose tissues and 3T3-L1 cells. Knockdown of LGI3 or ADAM23 by siRNA increased adipogenesis in 3T3-L1 cells. Treatment with LGI3 protein did not affect preadipocyte proliferation but attenuated adipogenesis and this effect was reversed by siRNA-mediated knockdown of ADAM23. Taken together, we propose that LGI3 may be a candidate adipokine that is perturbed in obesity and suppresses adipogenesis through its receptor, ADAM23. [Copyright &y& Elsevier]

Abstract: Leucine-rich glioma inactivated 3 (LGI3) is a member of LGI/epitempin family of which the first member, LGI1/epitempin, was shown to be mutated in glioma and autosomal dominant lateral temporal epilepsy. Similar to LGI1, LGI3 is expressed predominantly in brain and its function is unknown. In this study, we examined the expression of mouse LGI3 (mLGI3) in adult and developing brain and analyzed the 5′-upstream transcriptional regulatory regions of mLGI3 gene. In situ hybridization showed that mLGI3 was expressed in widespread areas with selective regional variation in adult brain. In developing brain, mLGI3 mRNA was expressed at low level during embryo stages and markedly increased in broad areas after birth. Analysis of the 5′- and 3′-ends of mLGI3 mRNA identified a single transcription start site and two alternative 3′-ends. Luciferase reporter analysis using Neuro-2a cells and electrophoretic mobility shift assays identified a neuronal restrictive silencer element (NRSE; −2573∼−2553) and a phorbol ester-sensitive AP-2 element with repressor activity (−44∼−33) among multiple positive and negative regulatory regions. Since NRSE and AP-2 are implicated in neuron-specific gene expression and developmental regulation of many genes in brain, respectively, these results suggested that NRSE and AP-2 might play important roles in regulation of mLGI3 expression in brain. [Copyright &y& Elsevier]