scholarly journals MTP regulated by an alternate promoter is essential for NKT cell development

2007 ◽  
Vol 204 (3) ◽  
pp. 533-545 ◽  
Author(s):  
Stephanie K. Dougan ◽  
Paul Rava ◽  
M. Mahmood Hussain ◽  
Richard S. Blumberg
Keyword(s):  
Lipid Transfer Protein ◽  
Microsomal Triglyceride Transfer Protein ◽  
Cell Development ◽  
Northern Analysis ◽  
Lipid Transfer ◽  
Nkt Cell ◽  
Transfer Protein ◽  
Phospholipid Transfer ◽  
Apob Secretion

Microsomal triglyceride transfer protein (MTP), an endoplasmic reticulum lipid transfer protein critical for apolipoprotein B (apoB) secretion, regulates CD1d antigen presentation. We identified MTP variant 1 (MTPv1), a novel splice variant of mouse MTP, by polymerase chain reaction and Northern analysis in non–apoB-secreting tissues, including thymocytes and antigen-presenting cells (APCs). Edman degradation of MTPv1 isolated from transfected cells revealed three unique residues; however, recombinant MTP and MTPv1 had an equivalent protein disulfide isomerase association, subcellular localization, triglyceride transfer, phospholipid transfer, response to inhibitors, and ability to support apoB secretion. MTP and MTPv1 efficiently transferred phosphatidylethanolamine to CD1d in vitro. NKT cells fail to develop in fetal thymic organ culture (FTOC) treated with MTP antagonists. MTP-inhibited FTOCs produced negligible numbers of CD1d tetramer–positive cells and exhibited marked defects in IL-4 production upon stimulation with anti-CD3 or α-galactosylceramide–pulsed APCs. CD1d expression on CD4+CD8+ FTOC cells was unaffected by MTP inhibition. Thus, our results demonstrate that MTPv1 in thymocytes is critical to NKT cell development. We hypothesize that, when MTP is inactive, CD1d traffics to the cell surface and presents no lipid or a lipid that is incapable of mediating NKT cell selection and/or is refractory to lysosomal editing.

scholarly journals Phospholipid transfer proteins revisited

1997 ◽  
Vol 324 (2) ◽  
pp. 353-360 ◽  
Author(s):  
Karel. W. A WIRTZ
Keyword(s):  
Mammalian Cells ◽  
Lipid Transfer Protein ◽  
Fusion Reaction ◽  
Lipid Binding ◽  
Lipid Transfer ◽  
Cell Functions ◽  
Transfer Protein ◽  
Phospholipid Transfer ◽  
Phosphatidylinositol Transfer

Phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) (identical with sterol carrier protein 2) belong to the large and diverse family of intracellular lipid-binding proteins. Although these two proteins may express a comparable phospholipid transfer activity in vitro, recent studies in yeast and mammalian cells have indicated that they serve completely different functions. PI-TP (identical with yeast SEC14p) plays an important role in vesicle flow both in the budding reaction from the trans-Golgi network and in the fusion reaction with the plasma membrane. In yeast, vesicle budding is linked to PI-TP regulating Golgi phosphatidylcholine (PC) biosynthesis with the apparent purpose of maintaining an optimal PI/PC ratio of the Golgi complex. In mammalian cells, vesicle flow appears to be dependent on PI-TP stimulating phosphatidylinositol 4,5-bisphosphate (PIP2) synthesis. This latter process may also be linked to the ability of PI-TP to reconstitute the receptor-controlled PIP2-specific phospholipase C activity. The nsL-TP is a peroxisomal protein which, by its ability to bind fatty acyl-CoAs, is most likely involved in the β-oxidation of fatty acids in this organelle. This protein constitutes the N-terminus of the 58 kDa protein which is one of the peroxisomal 3-oxo-acyl-CoA thiolases. Further studies on these and other known phospholipid transfer proteins are bound to reveal new insights in their important role as mediators between lipid metabolism and cell functions.

scholarly journals The Medicago truncatula N5 Gene Encoding a Root-Specific Lipid Transfer Protein Is Required for the Symbiotic Interaction with Sinorhizobium meliloti

2009 ◽  
Vol 22 (12) ◽  
pp. 1577-1587 ◽  
Author(s):  
Youry Pii ◽  
Alessandra Astegno ◽  
Elisa Peroni ◽  
Massimo Zaccardelli ◽  
Tiziana Pandolfini ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Lipid Transfer Protein ◽  
Symbiotic Association ◽  
Lipid Transfer ◽  
Symbiotic Interaction ◽  
Transgenic Roots ◽  
Transfer Protein ◽  
Small Proteins

The Medicago truncatula N5 gene is induced in roots after Sinorhizobium meliloti infection and it codes for a putative lipid transfer protein (LTP), a family of plant small proteins capable of binding and transferring lipids between membranes in vitro. Various biological roles for plant LTP in vivo have been proposed, including defense against pathogens and modulation of plant development. The aim of this study was to shed light on the role of MtN5 in the symbiotic interaction between M. truncatula and S. meliloti. MtN5 cDNA was cloned and the mature MtN5 protein expressed in Escherichia coli. The lipid binding capacity and antimicrobial activity of the recombinant MtN5 protein were tested in vitro. MtN5 showed the capacity to bind lysophospholipids and to inhibit M. truncatula pathogens and symbiont growth in vitro. Furthermore, MtN5 was upregulated in roots after infection with either the fungal pathogen Fusarium semitectum or the symbiont S. meliloti. Upon S. meliloti infection, MtN5 was induced starting from 1 day after inoculation (dpi). It reached the highest concentration at 3 dpi and it was localized in the mature nodules. MtN5-silenced roots were impaired in nodulation, showing a 50% of reduction in the number of nodules compared with control roots. On the other hand, transgenic roots overexpressing MtN5 developed threefold more nodules with respect to control roots. Here, we demonstrate that MtN5 possesses biochemical features typical of LTP and that it is required for the successful symbiotic association between M. truncatula and S. meliloti.

scholarly journals Biochemical analysis of antimicrobial peptides in two different Capsicum genotypes after fruit infection by Colletotrichum gloeosporioides

2019 ◽  
Vol 39 (4) ◽  
Author(s):  
Álan C. Maracahipes ◽  
Gabriel B. Taveira ◽  
Erica O. Mello ◽  
André O. Carvalho ◽  
Rosana Rodrigues ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Colletotrichum Gloeosporioides ◽  
Protein Extraction ◽  
Lipid Transfer Protein ◽  
Extraction Process ◽  
Lipid Transfer ◽  
Protease Inhibition ◽  
Transfer Protein ◽  
Trypsin Inhibition

Abstract There are several phytosanitary problems that have been causing serious damage to the Capsicum crops, including anthracnose. Upon attack by certain pathogens, various protein molecules are produced, which are known as proteins related to pathogenesis (PR proteins), including antimicrobial peptides such as protease inhibitors, defensins and lipid transfer proteins (LTPs). The objective of this work is to identify antimicrobial proteins and/or peptides of two genotypes from Capsicum annuum fruits infected with Colletotrichum gloeosporioides. The fungus was inoculated into Capsicum fruits by the deposition of a spore suspension (106 conidia ml−1), and after 24 and 48 h intervals, the fruits were removed from the humid chamber and subjected to a protein extraction process. Protein analysis of the extracts was performed by tricine gel electrophoresis and Western blotting. The distinctive bands between genotypes in the electrophoresis profiles were subjected to mass spectrometry sequencing. Trypsin inhibition assays, reverse zymographic detection of protease inhibition and β-1,3-glucanase activity assays were also performed and extracts were also tested for their ability to inhibit the growth of C. gloeosporioides fungi ‘in vitro’. There were several low molecular weight proteins in all treated samples, and some treatments in which antimicrobial peptides such as defensin, lipid transfer protein (LTP) and protease inhibitor have been identified. It was shown that the green fruits are more responsive to infection, showing the production of antimicrobial peptides in response to injury and inoculation of the fungus, what did not occur in ripe fruits under any treatment.

Lipid transfer protein isolated from noni seeds displays antibacterial activity in vitro and improves survival in lethal sepsis induced by CLP in mice

Biochimie ◽  
2018 ◽  
Vol 149 ◽  
pp. 9-17 ◽  
Author(s):  
Adson A. Souza ◽  
Andrea S. Costa ◽  
Dyély C.O. Campos ◽  
Andressa H.M. Batista ◽  
Gleilton W.P. Sales ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Lipid Transfer Protein ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Lethal Sepsis

Lipoprotein assembly and function in an evolutionary perspective

2010 ◽  
Vol 1 (2) ◽  
pp. 165-183 ◽  
Author(s):  
Dick J. Van der Horst ◽  
Kees W. Rodenburg
Keyword(s):  
Lipid Transfer Protein ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Microsomal Triglyceride Transfer Protein ◽  
Lipid Binding ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Density Lipoprotein Receptor ◽  
Exchangeable Basis ◽  
And Function

AbstractCirculatory fat transport in animals relies on members of the large lipid transfer protein (LLTP) superfamily, including mammalian apolipoprotein B (apoB) and insect apolipophorin II/I (apoLp-II/I). ApoB and apoLp-II/I, constituting the structural (non-exchangeable) basis for the assembly of various lipoproteins, acquire lipids through microsomal triglyceride-transfer protein, another LLTP family member, and bind them by means of amphipathic α-helical and β-sheet structural motifs. Comparative research reveals that LLTPs evolved from the earliest animals and highlights the structural adaptations in these lipid-binding proteins. Thus, in contrast to apoB, apoLp-II/I is cleaved post-translationally by a furin, resulting in the appearance of two non-exchangeable apolipoproteins in the single circulatory lipoprotein in insects, high-density lipophorin (HDLp). The remarkable structural similarities between mammalian and insect lipoproteins notwithstanding important functional differences relate to the mechanism of lipid delivery. Whereas in mammals, partial delipidation of apoB-containing lipoproteins eventually results in endocytic uptake of their remnants, mediated by members of the low-density lipoprotein receptor (LDLR) family, and degradation in lysosomes, insect HDLp functions as a reusable lipid shuttle capable of alternate unloading and reloading of lipid. Also, during muscular efforts (flight activity), an HDLp-based lipoprotein shuttle provides for the transport of lipid for energy generation. Although a lipophorin receptor – a homolog of LDLR – was identified that mediates endocytic uptake of HDLp during specific developmental periods, the endocytosed lipoprotein appears to be recycled in a transferrin-like manner. These data highlight that the functional adaptations in the lipoprotein lipid carriers in mammals and insects also emerge with regard to the functioning of their cognate receptors.

scholarly journals Microsomal triglyceride transfer protein lipidation and control of CD1d on antigen-presenting cells

2005 ◽  
Vol 202 (4) ◽  
pp. 529-539 ◽  
Author(s):  
Stephanie K. Dougan ◽  
Azucena Salas ◽  
Paul Rava ◽  
Amma Agyemang ◽  
Arthur Kaser ◽  
...  
Keyword(s):  
Mononuclear Cells ◽  
Microsomal Triglyceride Transfer Protein ◽  
Antigen Presenting Cells ◽  
Human Monocyte ◽  
Lipid Transfer ◽  
Mouse Splenocytes ◽  
Transfer Protein ◽  
Er Chaperone ◽  
Antigen Presenting

Microsomal triglyceride transfer protein (MTP), an endoplasmic reticulum (ER) chaperone that loads lipids onto apolipoprotein B, also regulates CD1d presentation of glycolipid antigens in the liver and intestine. We show MTP RNA and protein in antigen-presenting cells (APCs) by reverse transcription–polymerase chain reaction and by immunoblotting of mouse liver mononuclear cells and mouse and human B cell lines. Functional MTP, demonstrated by specific triglyceride transfer activity, is present in both mouse splenocytes and a CD1d-positive mouse NKT hybridoma. In a novel in vitro transfer assay, purified MTP directly transfers phospholipids, but not triglycerides, to recombinant CD1d. Chemical inhibition of MTP lipid transfer does not affect major histocompatibility complex class II presentation of ovalbumin, but considerably reduces CD1d-mediated presentation of α-galactosylceramide (α-galcer) and endogenous antigens in mouse splenic and bone marrow–derived dendritic cells (DCs), as well as in human APC lines and monocyte-derived DCs. Silencing MTP expression in the human monocyte line U937 affects CD1d function, as shown by diminished presentation of α-galcer. We propose that MTP acts upstream of the saposins and functions as an ER chaperone by loading endogenous lipids onto nascent CD1d. Furthermore, our studies suggest that a small molecule inhibitor could be used to modulate the activity of NKT cells.

In vivo and in vitro techniques in the diagnosis of lipid transfer protein sensitization

2013 ◽  
Vol 111 (6) ◽  
pp. 571-573 ◽  
Author(s):  
Felicia Berroa ◽  
Gabriel Gastaminza ◽  
Noemí Saiz ◽  
Julián Azofra ◽  
Pedro M. Gamboa ◽  
...  
Keyword(s):  
Lipid Transfer Protein ◽  
Lipid Transfer ◽  
In Vitro Techniques ◽  
Transfer Protein ◽  
Protein Sensitization

Abstract 192: Characterization of Microsomal Triglyceride Transfer Protein Missense Mutations Found in Abetalipoproteinemia and Hybobetalipoproteinemia Subjects

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Meghan T Walsh ◽  
Enza Di Leo ◽  
Patrizia Tarugi ◽  
M. Mahmood Hussain
Keyword(s):  
Plasma Lipid ◽  
Microsomal Triglyceride Transfer Protein ◽  
The Other ◽  
Plasma Lipoproteins ◽  
Missense Mutations ◽  
Lipid Transfer ◽  
Novel Proteins ◽  
Transfer Protein ◽  
Apob Secretion ◽  
Familial Hypobetalipoproteinemia

We describe two new hypolipidemic patients with very low plasma triglyceride and apolipoprotein B (apoB) levels and lipid malabsorption with plasma lipid profiles similar to abetalipoproteinemia (ABL) patients. In these patients, we identified two previously uncharacterized missense mutations in the microsomal triglyceride transfer protein (MTP) gene, R46G and D361Y, and studied their effects on function. We also characterized three missense mutations (H297Q, D384A, and G661A) reported earlier in a familial hypobetalipoproteinemia patient. R46G had no effect on MTP expression or function and supported apoB secretion. Similarly, H297Q, D384A, and G661A mutants supported apoB secretion similarly to WT MTP. Contrary to these four missense mutations, D361Y was unable to support apoB secretion. Functional analysis revealed that this mutant was unable to bind protein disulfide isomerase (PDI) or transfer lipids. The negative charge at residue 361 was critical for MTP function as D361E was able to support apoB secretion and transfer lipids. D361Y most likely disrupts the tightly packed middle α-helical region of MTP, mitigates PDI binding, abolishes lipid transfer activity, and causes ABL. On the other hand, the hypolipidemia in the other two patients was not due to MTP dysfunction. Thus, in this study of five missense mutations spread throughout MTP’s three structural domains found in three hypolipidemic patients, we found that four of the mutations did not affect MTP function. Thus, there probably exist novel mutations in other genes that cause severe hypolipidemia and their recognition may identify novel proteins involved in the synthesis and/or catabolism of plasma lipoproteins.

scholarly journals Noncanonical regulation of phosphatidylserine metabolism by a Sec14-like protein and a lipid kinase

2020 ◽  
Vol 219 (5) ◽  
Author(s):  
Yaxi Wang ◽  
Peihua Yuan ◽  
Aby Grabon ◽  
Ashutosh Tripathi ◽  
Dongju Lee ◽  
...  
Keyword(s):  
Lipid Transfer Protein ◽  
Physical Interaction ◽  
Lipid Transfer ◽  
Uncharacterized Protein ◽  
Lipid Kinase ◽  
Transfer Protein ◽  
Transfer Activity ◽  
Phosphatidylinositol Transfer

The yeast phosphatidylserine (PtdSer) decarboxylase Psd2 is proposed to engage in a membrane contact site (MCS) for PtdSer decarboxylation to phosphatidylethanolamine (PtdEtn). This proposed MCS harbors Psd2, the Sec14-like phosphatidylinositol transfer protein (PITP) Sfh4, the Stt4 phosphatidylinositol (PtdIns) 4-OH kinase, the Scs2 tether, and an uncharacterized protein. We report that, of these components, only Sfh4 and Stt4 regulate Psd2 activity in vivo. They do so via distinct mechanisms. Sfh4 operates via a mechanism for which its PtdIns-transfer activity is dispensable but requires an Sfh4-Psd2 physical interaction. The other requires Stt4-mediated production of PtdIns-4-phosphate (PtdIns4P), where Stt4 (along with the Sac1 PtdIns4P phosphatase and endoplasmic reticulum–plasma membrane tethers) indirectly modulate Psd2 activity via a PtdIns4P homeostatic mechanism that influences PtdSer accessibility to Psd2. These results identify an example in which the biological function of a Sec14-like PITP is cleanly uncoupled from its canonical in vitro PtdIns-transfer activity and challenge popular functional assumptions regarding lipid-transfer protein involvements in MCS function.

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