A Peptide Derived from the Intercellular Adhesion Molecule-2 Regulates the Avidity of the Leukocyte Integrins CD11b/CD18 and CDllc/CD18

β2 integrin (CDlla,b,c/CD18)-mediated cell adhesion is required for many leukocyte functions. Under normal circumstances, the integrins are nonadhesive, and become adhesive for their cell surface ligands, the intercellular adhesion molecules (ICAMs), or soluble ligands such as fibrinogen and iC3b, when leukocytes are activated. Recently, we defined a peptide derived from ICAM-2, which specifically binds to purified CDlla/CD18. Furthermore, this peptide strongly induces T cell aggregation mainly mediated by CDlla/CD18-ICAM-1 interaction, and natural killer cell cytotoxicity. In the present study, we show that the same ICAM-2 peptide also avidly binds to purified CDllb/CD18, but not to CDllc/CD18. This binding can be blocked by the CD1 lb antibody OKM10. The peptide strongly stimulates CDllb/CD18-ICAM-l-mediated cell aggregations of the monocytic cell lines THP-1 and U937. The aggregations are energy and divalent cation-dependent. The ICAM-2 peptide also induces CDllb/CD18 and CDllc/CD18-mediated binding of THP-1 cells to fibrinogen and iC3b coated on plastic. These findings indicate that in addition to induction of CDlla/CD18- mediated cell adhesion, the ICAM-2 peptide may also serve as a "trigger" for high avidity ligand binding of other β2 integrins

Angiopoietin-Like 4 Mediates PPAR Delta Effect on Lipoprotein Lipase-Dependent Fatty Acid Uptake but Not on Beta-Oxidation in Myotubes

Peer reviewe

Comparative study of sugar fermentation and protein expression patterns of two Lactobacillus plantarum strains grown in three Different Media

v2008okBEL/BM

Polymorphism and deficiency of human factor H-related proteins p39 and p37

We described previously cDNA clones representing a novel factor H-related 1.4 kilobase mRNA. This mRNA species codes for a doublet of serum proteins of M(r) 39 000 and 37 000 (p39/p37). The respective recombinant proteins of the three clones H-69, pFH1.4a, and pFH1.4b differ in the expression of the epitope recognized by the monoclonal antibody (mAb) 3D11. This probably reflects the difference of three amino acid residues of the deduced protein sequence. Here we report evidence for corresponding alterations in the native proteins p39/p37 in human sera. Employing mAb 3D11 and a polyclonal factor H-specific antiserum we detected three different patterns in western blot analyses of human sera which we provisionally termed FH1.4p+m+, FH1.4p+m-, and FH1.4p-m-. In the first pattern, p39/p37 were recognized by both antibodies, while in the second pattern the two proteins reacted only with the polyclonal antiserum. Both antibodies failed to detect p39/p37 in the third pattern. These phenotypes are found in the healthy population with frequencies of 0.556, 0.40, and 0.044, respectively. The frequencies of the alleles FH1.4(*)p+m+, FH1.4(*)p+m -,and FH1.4(*)p-m- were estimated to be 0.33, 0.46, and 0.21, respectively, assuming the gene distribution to be in Hardy-Weinberg equilibrium. Studies of 98 members from 27 families revealed an autosomal Mendelian inheritance. Southern blot data support our assumption of a polymorphism of the factor H-related proteins p39 and p37

Finnish-specific AKT2 gene variant leads to impaired insulin signalling in myotubes

Finnish-specific gene variant p.P50T/AKT2 (minor allele frequency (MAF) = 1.1%) is associated with insulin resistance and increased predisposition to type 2 diabetes. Here, we have investigated in vitro the impact of the gene variant on glucose metabolism and intracellular signalling in human primary skeletal muscle cells, which were established from 14 male p.P50T/AKT2 variant carriers and 14 controls. Insulin-stimulated glucose uptake and glucose incorporation into glycogen were detected with 2-[1,2-H-3]-deoxy-D-glucose and D-[C-14]-glucose, respectively, and the rate of glycolysis was measured with a Seahorse XF(e)96 analyzer. Insulin signalling was investigated with Western blotting. The binding of variant and control AKT2-PH domains to phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P-3) was assayed using PIP Strips(TM) Membranes. Protein tyrosine kinase and serine-threonine kinase assays were performed using the PamGene (R) kinome profiling system. Insulin-stimulated glucose uptake and glycogen synthesis in myotubes in vitro were not significantly affected by the genotype. However, the insulin-stimulated glycolytic rate was impaired in variant myotubes. Western blot analysis showed that insulin-stimulated phosphorylation of AKT-Thr(308), AS160-Thr(642) and GSK3 beta-Ser(9) was reduced in variant myotubes compared to controls. The binding of variant AKT2-PH domain to PI(3,4,5)P-3 was reduced as compared to the control protein. PamGene (R) kinome profiling revealed multiple differentially phosphorylated kinase substrates, e.g. calmodulin, between the genotypes. Further in silico upstream kinase analysis predicted a large-scale impairment in activities of kinases participating, for example, in intracellular signal transduction, protein translation and cell cycle events. In conclusion, myotubes from p.P50T/AKT2 variant carriers show multiple signalling alterations which may contribute to predisposition to insulin resistance and T2D in the carriers of this signalling variant.Peer reviewe

Proposed mechanism regulating LPL activity in the skeletal muscle.

<p>The working hypothesis is that FAs produced locally by LPL-mediated hydrolysis of VLDL and chylomicrons (CM) together with FAs derived from adipose tissue (FA-albumin) can activate PPARδ/RXR heterodimer which in turn upregulates Angptl4 gene expression. Angptl4 inhibits LPL activity mainly at the surface of the sarcolemma where less LPL will be available to be transported at luminal sites via the function of GPIHBP1. LPL inhibition by Angptl4 occurs to a lesser extent also intracellularly. This mechanism may protect the skeletal muscle from lipid overload and insulin resistance but may also contribute to bexarotene induced systemic hypertriglyceridemia.</p