Regulation by a protein-free carbohydrate-rich diet of rat pancreatic mRNAs encoding trypsin and elastase isoenzymes.
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ABSTRACT:
SUBMITTER: Dakka N
PROVIDER: S-EPMC1131456 | biostudies-other | 1990 Jun
REPOSITORIES: biostudies-other
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Project description:Human pancreatic elastase 1 (E1) is a glycoprotein containing two potential N-glycosylation sites, one of which carries a carbohydrate moiety [Wendorf, Geyer, Sziegoleit & Linder (1989) FEBS Lett. 249, 275-278]. In order to study its glycosylation, glycoprotein isolated from post-mortem pancreas tissue of 75 donors was digested with trypsin. Oligosaccharides were liberated from resulting glycopeptides by treatment with peptide-N4-(N-acetyl-beta-glycosaminyl)-asparagine amidase F, radiolabelled by reduction with KB3H4 and separated by h.p.l.c. and gel filtration. Major oligosaccharide alditol fractions, representing 67.8 mol% of total glycans, were characterized by methylation analysis and sequential degradation with exoglycosidases. The results revealed that about two-fifths of the partially truncated, mainly biantennary, complex-type glycans found comprised blood group A, B, Lea (or X), difucosyl A or difucosyl B determinants, which could be assigned to lactosamine antennae linked to Man(alpha 1-3)- residues of the sugar chains.
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Project description:Cross-linking mass spectrometry has become an important approach for studying protein structures and protein-protein interactions. The amino acid compositions of some protein regions impede the detection of cross-linked residues, although it would yield invaluable information for protein modeling. Here, we report on a sequential-digestion strategy with trypsin and elastase to penetrate regions with a low density of trypsin-cleavage sites. We exploited intrinsic substrate-recognition properties of elastase to specifically target larger tryptic peptides. Our application of this protocol to the TAF4-12 complex allowed us to identify cross-links in previously inaccessible regions.
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Project description:BackgroundTransplantation of pancreatic β cells generated in vitro from pluripotent stem cells (hPSCs) such as embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) has been proposed as an alternative therapy for diabetes. Though many differentiation protocols have been developed for this purpose, lentivirus-mediated forced expression of transcription factors (TF)-PDX1 and NKX6.1-has been at the forefront for its relatively fast and straightforward approach. However, considering that such cells will be used for therapeutic purposes in the future, it is desirable to develop a procedure that does not leave any footprint on the genome, as any changes of DNAs could potentially be a source of unintended, concerning effects such as tumorigenicity. In this study, we attempted to establish a novel protocol for rapid and footprint-free hESC differentiation into a pancreatic endocrine lineage by using synthetic mRNAs (synRNAs) encoding PDX1 and NKX6.1. We also tested whether siPOU5F1, which reduces the expression of pluripotency gene POU5F1 (also known as OCT4), can enhance differentiation as reported previously for mesoderm and endoderm lineages.MethodssynRNA-PDX1 and synRNA-NKX6.1 were synthesized in vitro and were transfected five times to hESCs with a lipofection reagent in a modified differentiation culture condition. siPOU5F1 was included only in the first transfection. Subsequently, cells were seeded onto a low attachment plate and aggregated by an orbital shaker. At day 13, the degree of differentiation was assessed by quantitative RT-PCR (qRT-PCR) and immunohistochemistry for endocrine hormones such as insulin, glucagon, and somatostatin.ResultsBoth PDX1 and NKX6.1 expression were detected in cells co-transfected with synRNA-PDX1 and synRNA-NKX6.1 at day 3. Expression levels of insulin in the transfected cells at day 13 were 450 times and 14 times higher by qRT-PCR compared to the levels at day 0 and in cells cultured without synRNA transfection, respectively. Immunohistochemically, pancreatic endocrine hormones were not detected in cells cultured without synRNA transfection but were highly expressed in cells transfected with synRNA-PDX1, synRNA-NKX6.1, and siPOU5F1 at as early as day 13.ConclusionsIn this study, we report a novel protocol for rapid and footprint-free differentiation of hESCs to endocrine cells.
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Project description:Determination of fecal pancreatic elastase content by ELISA is a reliable, noninvasive clinical test for assessing exocrine pancreatic function. Despite the widespread use of commercial tests, their exact molecular targets remain poorly characterized. This study was undertaken to clarify which human pancreatic elastase isoforms are detected by the ScheBo Pancreatic Elastase 1 Stool Test and whether naturally occurring genetic variants influence the performance of this test. Using recombinantly expressed and purified human pancreatic proteinases, we found that the test specifically measured chymotrypsin-like elastases (CELA) 3A and 3B (CELA3A and CELA3B), while CELA2A was not detected. Inactive proelastases, active elastases, and autolyzed forms were detected with identical efficiency. CELA3B elicited approximately four times higher ELISA signal than CELA3A, and we identified Glu154 in CELA3B as the critical determinant of detection. Common genetic variants of CELA3A and CELA3B had no effect on test performance, with the exception of the CELA3B variant W79R, which increased detection by 1.4-fold. Finally, none of the human trypsin and chymotrypsin isoforms were detected. We conclude that the ScheBo Pancreatic Elastase 1 Stool Test is specific for human CELA3A and CELA3B, with most of the ELISA signal attributable to CELA3B.NEW & NOTEWORTHY The ScheBo Pancreatic Elastase 1 Stool Test is widely used to assess pancreatic exocrine function, yet its molecular targets have been poorly defined. We demonstrate that, among the human pancreatic proteinases, the test measures the elastase isoform CELA3B and, to a lesser extent, CELA3A. Genetic variants of the human CELA3 isoforms have no significant effect on test performance.
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Project description:Translation-independent mRNA localization represents an emerging concept in cell biology. In Escherichia coli, mRNAs encoding integral membrane proteins (MPRs) are targeted to the membrane where they are translated by membrane associated ribosomes and the produced proteins are inserted into the membrane co-translationally. In order to better understand aspects of the biogenesis and localization of MPRs, we investigated their subcellular distribution using cell fractionation, RNA-seq and qPCR. The results show that MPRs are overrepresented in the membrane fraction, as expected, and depletion of the signal recognition particle-receptor, FtsY reduced the amounts of all mRNAs on the membrane. Surprisingly, however, MPRs were also found relatively abundant in the soluble ribosome-free fraction and their amount in this fraction is increased upon overexpression of CspE, which was recently shown to interact with MPRs. CspE also conferred a positive effect on the membrane-expression of integral membrane proteins. We discuss the possibility that the effects of CspE overexpression may link the intriguing subcellular localization of MPRs to the cytosolic ribosome-free fraction with their translation into membrane proteins and that the ribosome-free pool of MPRs may represent a stage during their targeting to the membrane, which precedes translation.
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Project description:Aromatic side chains (phenylalanine and tyrosine) of a protein flip by 180° around the Cβ-Cγ axis (χ2 dihedral of the side chain), producing two symmetry-equivalent states. The study of ring flip dynamics with nuclear magnetic resonance (NMR) experiments helps to understand local conformational fluctuations. Ring flips are categorized as slow (milliseconds and onward) or fast (nanoseconds to near milliseconds) based on timescales accessible to NMR experiments. In this study, we investigated the ability of the infrequent metadynamics approach to estimate the flip rate and discriminate between slow and fast ring flips for eight individual aromatic side chains (F4, Y10, Y21, F22, Y23, F33, Y35, and F45) of the basic pancreatic trypsin inhibitor. Well-tempered metadynamics simulations were performed to estimate the ring-flipping free-energy surfaces for all eight aromatic residues. The results indicate that χ2 as a standalone collective variable (CV) is not sufficient to obtain computationally consistent results. Inclusion of a complementary CV, such as χ1(Cα-Cβ), solved the problem for most residues and enabled us to classify fast and slow ring flips. This indicates the importance of librational motions in ring flips. Multiple pathways and mechanisms were observed for residues F4, Y10, and F22. Recrossing events were observed for residues F22 and F33, indicating a possible role of friction effects in ring flipping. The results demonstrate the successful application of infrequent metadynamics to estimate ring flip rates and identify certain limitations of the approach.
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Project description: Not available
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2021-09-09 | PXD017786 | Pride