scholarly journals Human inter-α-trypsin inhibitor. Synthesis and maturation in hepatoma HepG2 cells

1989 ◽  
Vol 261 (1) ◽  
pp. 305-308 ◽  
Author(s):  
J Bourguignon ◽  
R Sesboüé ◽  
M Diarra-Mehrpour ◽  
M Daveau ◽  
J P Martin
Keyword(s):  
Trypsin Inhibitor ◽  
Light Chain ◽  
Hepg2 Cells ◽  
Light Chains ◽  
Limiting Factor ◽  
Heavy Chains ◽  
Chain Synthesis ◽  
Hepatoma Hepg2

In hepatoma HepG2 cells, human inter-alpha-trypsin inhibitor (ITI) was synthesized as three heavy chains, H-1 (100 kDa), H-2 (110 kDa) and H-3 (113 kDa), and light hybrid chain (49.5 kDa) composed of alpha 1-microglobulin and HI-30 (ITI derivative, human inhibitor of 30 kDa). The association of at least two heavy chains, H-1 and H-3, with the HI-30 part of the light chain gave rise to a molecule similar to serum ITI. A composite protein (approximately 250 kDa) including heavy and light chains was also secreted, while alpha 1-microglobulin and ITI H-2 protein were released as separate entities. Light chain synthesis could be the limiting factor for ITI maturation.

scholarly journals Post-translational processing of the inter-α-trypsin inhibitor in the human hepatoma HepG2 cell line

1994 ◽  
Vol 302 (2) ◽  
pp. 573-580 ◽  
Author(s):  
A Héron ◽  
J Bourguignon ◽  
A Callé ◽  
H Borghi ◽  
R Sesboüé ◽  
...  
Keyword(s):  
Heavy Chain ◽  
Trypsin Inhibitor ◽  
Hepg2 Cells ◽  
Chondroitin Sulphate ◽  
Brefeldin A ◽  
Human Hepatoma ◽  
Heavy Chains ◽  
Human Hepatoma Hepg2 Cells ◽  
Golgi Network ◽  
Hepatoma Hepg2

In human hepatoma HepG2 cells, the serum inter-alpha-trypsin inhibitor (ITI)-like protein is synthesized from two protein precursors, the heavy chain (H) H2 and the light chain (L). Both of them carry sulphate groups involved in the chondroitin sulphate glycosaminoglycan (GAG) linkage, as demonstrated by [35S]sulphate labelling, chondroitinase digestion and inhibition with beta-D-xyloside, an artificial GAG acceptor. While inhibition of N-glycosylation prevented neither the maturation nor the secretion of the ITI-related entities, brefeldin A induced the accumulation of H and L precursors in the cells, therefore blocking subsequent association and maturation of the precursors before their secretion. The enzyme system involved in the ester linkage between H and L chains is localized in the trans-Golgi network since no ITI-like protein could be obtained in the presence of monensin; instead free heavy-chain protein forms and bikunin were secreted in culture supernatants. The ITI-like protein synthesized by HepG2 cells is therefore composed of two heavy chains HC2 linked to two bikunin chains by chondroitin sulphate bridges, although the GAG linkage between HC2 chains is presumably different. Further, a different maturation route leading to restricted heavy-chain forms, Hm and Hd, could be shown.

scholarly journals BiP and Immunoglobulin Light Chain Cooperate to Control the Folding of Heavy Chain and Ensure the Fidelity of Immunoglobulin Assembly

1999 ◽  
Vol 10 (7) ◽  
pp. 2209-2219 ◽  
Author(s):  
Young-Kwang Lee ◽  
Joseph W. Brewer ◽  
Rachel Hellman ◽  
Linda M. Hendershot
Keyword(s):  
Heavy Chain ◽  
Light Chain ◽  
Protein Complexes ◽  
Critical Role ◽  
Light Chains ◽  
Heavy Chains ◽  
Chain Complexes ◽  
Chain Synthesis

The immunoglobulin (Ig) molecule is composed of two identical heavy chains and two identical light chains (H2L2). Transport of this heteromeric complex is dependent on the correct assembly of the component parts, which is controlled, in part, by the association of incompletely assembled Ig heavy chains with the endoplasmic reticulum (ER) chaperone, BiP. Although other heavy chain-constant domains interact transiently with BiP, in the absence of light chain synthesis, BiP binds stably to the first constant domain (CH1) of the heavy chain, causing it to be retained in the ER. Using a simplified two-domain Ig heavy chain (VH-CH1), we have determined why BiP remains bound to free heavy chains and how light chains facilitate their transport. We found that in the absence of light chain expression, the CH1 domain neither folds nor forms its intradomain disulfide bond and therefore remains a substrate for BiP. In vivo, light chains are required to facilitate both the folding of the CH1 domain and the release of BiP. In contrast, the addition of ATP to isolated BiP–heavy chain complexes in vitro causes the release of BiP and allows the CH1 domain to fold in the absence of light chains. Therefore, light chains are not intrinsically essential for CH1 domain folding, but play a critical role in removing BiP from the CH1 domain, thereby allowing it to fold and Ig assembly to proceed. These data suggest that the assembly of multimeric protein complexes in the ER is not strictly dependent on the proper folding of individual subunits; rather, assembly can drive the complete folding of protein subunits.

scholarly journals Fate of surrogate light chains in B lineage cells.

1996 ◽  
Vol 183 (2) ◽  
pp. 421-429 ◽  
Author(s):  
K Lassoued ◽  
H Illges ◽  
K Benlagha ◽  
M D Cooper
Keyword(s):  
B Cells ◽  
Cell Surface ◽  
Light Chain ◽  
Light Chains ◽  
Receptor Complex ◽  
Surrogate Light Chain ◽  
Heavy Chains ◽  
Receptor Component ◽  
B Lineage ◽  
Receptor Assembly

Biosynthesis of the immunoglobulin (Ig) receptor components and their assembly were examined in cell lines representative of early stages in human B lineage development. In pro-B cells, the nascent surrogate light chain proteins form a complex that transiently associates in the endoplasmic reticulum with a spectrum of unidentified proteins (40, 60, and 98 kD) and Bip, a heat shock protein family member. Lacking companion heavy chains, the surrogate light chains in pro-B cells do not associate with either the Ig(alpha) or Ig(beta) signal transduction units, undergo rapid degradation, and fail to reach the pro-B cell surface. In pre-B cells, by contrast, a significant portion of the surrogate light chain proteins associate with mu heavy chains, Ig(alpha), and Ig(beta) to form a stable receptor complex with a relatively long half-life. Early in this assembly process, Bip/GRP78, calnexin, GRP94, and a protein of approximately 17 kD differentially bind to the nascent mu heavy chains. The 17-kD intermediate is gradually replaced by the surrogate light chain protein complex, and the Ig(alpha) and Ig(beta) chains bind progressively to the mu heavy chains during the complex and relatively inefficient process of pre-B receptor assembly. The results suggest that, in humans, heavy chain association is essential for surrogate light chain survival and transport to the cell surface as an integral receptor component.

scholarly journals Relative synthesis of cardiac contractile proteins. Evidence for synthesis from the same precursor pool

1981 ◽  
Vol 194 (3) ◽  
pp. 673-678 ◽  
Author(s):  
C D Evans ◽  
S S Schreiber ◽  
M Oratz ◽  
M A Rothschild
Keyword(s):  
Light Chain ◽  
Contractile Proteins ◽  
Light Chains ◽  
Myosin Heavy Chains ◽  
Perfused Heart ◽  
Precursor Pool ◽  
Heavy Chains ◽  
Cardiac Contractile ◽  
Specific Activities ◽  
Cardiac Contractile Proteins

The relative molar synthesis of cardiac contractile proteins has been measured in the perfused heart under control haemodynamic conditions. This synthesis, of myosin heavy chains, individual light chains (1 and 2), actin and tropomyosin, was determined from isolated guinea-pig hearts perfused for 3h simultaneously with constant specific radioactivities and concentrations of [3H]lysine and [3H]phenylalanine.The data strongly suggest that all of the proteins studied were synthesized from the same precursor pools of lysine and phenylalanine, since the ratio of the specific activities of the two labels was the same in all of the proteins. Measurement of molar synthesis of each contractile protein was the same with either labelled amino acid. Under control haemodynamic-perfusion conditions, the relative molar synthesis of the contractile proteins was actin greater than heavy chains greater than light chain 2 greater than light chain 1 greater than tropomyosin.

scholarly journals Properties of the non-specific calcium-binding sites of rabbit skeletal-muscle myosin

1980 ◽  
Vol 185 (1) ◽  
pp. 265-268 ◽  
Author(s):  
J Wikman-Coffelt
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Binding Sites ◽  
Calcium Binding ◽  
Light Chains ◽  
Binding Properties ◽  
Skeletal Muscle Myosin ◽  
Heavy Chains ◽  
Calcium Binding Sites ◽  
Muscle Myosin

The non-specific Ca2+-binding sites of skeletal-muscle myosin are located on the light chains; with the dissociation of light chains there is a corresponding decrease in the number of Ca2+-binding sites on light-chain-deficient myosin. The released light chains have a decreased binding affinity. Myosin heavy chains indirectly influence the Ca2+-binding properties of light chains by increasing the affinity of light chains for bivalent cations; this influence varies with pH. Because of light-chain dissociation at low Ca2+ and/or Mg2+ concentrations, anomalies may exist when analyses of non-specific Ca2+-binding properties of myosin are assessed by dialysis equilibrium.

Inhibitory ADAMTS13 Monoclonal Autoantibodies Cloned from TTP Patients Show Restricted Gene Usage, Inhibit Murine ADAMTS13, and Are Blocked by Rabbit Anti-Idiotypic Antibodies.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 92-92 ◽  
Author(s):  
Don Siegel ◽  
Eric Ostertag
Keyword(s):  
Immune Response ◽  
Phage Display ◽  
Heavy Chain ◽  
Light Chain ◽  
Light Chains ◽  
Chain Gene ◽  
Human Mabs ◽  
Heavy Chains ◽  
Phage Display Libraries ◽  
Pathogenic Antibodies

Abstract Thrombotic thrombocytopenic purpura (TTP) is a potentially fatal disorder often associated with autoantibody inhibition of ADAMTS13, a VWF-cleaving protease. Autoantibodies decrease ADAMTS13 activity resulting in accumulation of “unusually” large VWF multimers that mediate platelet thrombosis. To better understand the role autoantibodies play in disease pathogenesis, as well as to develop more specific methods for diagnosis and therapy, it is necessary to characterize pathogenic antibodies on a molecular level, something not possible through analysis of polyclonal patient antisera. The ability to clone large repertoires of patient monoclonal autoantibodies (mAbs) using phage display offers a unique opportunity to address this issue. Three patient (Pt) antibody phage display libraries were created from either splenocytes (Pt1) or peripheral blood lymphocytes (Pt2, Pt3) of individuals with acquired TTP. ADAMTS13-specific mAbs were isolated by panning against recombinant ADAMTS13. Unique clones were identified by DNA sequencing, and their ability to interact with ADAMTS13 was characterized. After antigen selection of Pt1 library, 56 mAbs were randomly-selected from panning rounds 2 through 4 and 68% were found to comprise heavy chains encoded by VH1-69 paired with a VL3 family lambda light chain (3h or 3m). The remaining mAbs comprised heavy chains from the VH1, 3, or 4 families usually paired with kappa light chains. For Pt2 and Pt3 libraries, there was an identical pattern of genetic restriction in immune response to ADAMTS13, i.e. 16 of 24 mAbs (Pt2) and 27 of 27 mAbs (Pt3) were encoded by VH1-69 heavy chains and VL3 family lambda light chains. Though nearly all mAbs were unique, common CDR3 regions among some of the mAbs provided evidence of B-cell clonal expansion and somatic mutation. Though all mAbs bound to ADAMTS13 irrespective of genetic origin, mAbs comprising a VH1-69 heavy chain paired with a VL3 light chain inhibited ADAMTS13 using the FRET-VW73 assay while mAbs comprising a VH1-69 paired with a kappa light chain or comprising non-VH1-69 heavy chains did not inhibit ADAMTS13, with only two exceptions. MAb binding to ADAMTS13 was blocked by preincubation with normal human or murine plasma, but much less so by plasma from TTP patients or ADAMTS13 knockout mice suggesting crossreactivity with mouse ADAMTS13. Certain human mAbs inhibited cleavage of FRET-VWF73 by mouse ADAMTS13 and also inhibited ADAMTS13 in vivo after injection into the internal jugular vein of mice. Rabbit anti-idiotypic antibodies raised against mAb 416, a prototypical VH1-69-encoded mAb, blocked 416’s ability to inhibit human ADAMTS13. Taken together, the cloning and analyses of a large cohort of ADAMTS13 inhibitory autoantibodies derived from 3 unrelated individuals with acquired TTP revealed a genetically restricted immune response. This feature, if common among TTP patients, offers a potential therapeutic target for treatment of TTP, e.g. selective deletion of B-cells utilizing the VH1-69 heavy chain gene. Furthermore, crossreactivity of some human mAbs with murine ADAMTS13 provides a mouse model of acquired ADAMTS13 deficiency that may prove useful for determining the role of autoantibodies in the pathogenesis of TTP, particularly in the context of additional factors (e.g. environmental) that may be required to trigger the disease. Finally, anti-idiotypic mAbs, currently being cloned from rabbit phage display libraries, may help identify pathogenic antibodies in patient plasma and/or lead to novel therapeutic approaches.

Biosynthesis of immunoglobulins on polyribosomes and assembly of the IgG molecule

1966 ◽  
Vol 166 (1003) ◽  
pp. 232-243 ◽  
Keyword(s):  
Light Chain ◽  
Gradient Centrifugation ◽  
Intermediate Stage ◽  
Light Chains ◽  
Pulse Labelling ◽  
Myeloma Protein ◽  
Heavy Chains ◽  
Specific Antisera ◽  
Independent Synthesis ◽  
Small Pool

Immunoglobulin G formation was studied using as model system an ascitic form of the murine plasmacytom 5563. Following pulse labelling of the cells with 3 H-leucine, polyribosomes were fractionated on sucrose gradients. By the use of antisera specific for various parts of the IgG molecule, nascent heavy and light chains were detected on distinct polyribosomes of different size. Polyribosomes carrying heavy chain determinants were present in clusters with maximum sedimentation constants of around 300 S.; a much lower proportion of radioactivity was detectable as light chain determinants on polyribosomes up to 200 S. This observation is consistent with the independent synthesis of each chain as one polypeptide unit. Release of light chains appears to be an intermediate stage in the assembly of the IgG molecule. After pulse labelling of cells soluble IgG determinants were analysed by sucrose gradient centrifugation and precipitation with specific antisera. Only the light chains were released into a small pool which may control the release of heavy chains from polyribosomes. The radioactivity of the light chain pool reached a maximum at 10 min, whereas that of whole myeloma protein increased linearly with time. These results fit the interpretation that light chains form a small, rapidly turning over, pool before being incorporated into whole IgG molecules.

One siRNA pool targeting the λ constant region stops λ light-chain production and causes terminal endoplasmic reticulum stress

Blood ◽  
2014 ◽  
Vol 123 (22) ◽  
pp. 3440-3451 ◽  
Author(s):  
Ping Zhou ◽  
Xun Ma ◽  
Lakshmanan Iyer ◽  
Chakra Chaulagain ◽  
Raymond L. Comenzo
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Stress ◽  
Light Chain ◽  
Antibody Production ◽  
Plasma Cells ◽  
Light Chains ◽  
Constant Region ◽  
Immunoglobulin Light Chain ◽  
Heavy Chains ◽  
Key Points

Key PointsImmunoglobulin light-chain and antibody production by plasma cells is significantly reduced by siRNA for the light-chain constant region. In plasma cells making intact antibodies, knockdown of light chains can cause terminal ER stress because of unpaired heavy chains.

An isoform of kinesin light chain specific for the Golgi complex

2000 ◽  
Vol 113 (11) ◽  
pp. 2047-2054
Author(s):  
F.K. Gyoeva ◽  
E.M. Bybikova ◽  
A.A. Minin
Keyword(s):  
Golgi Complex ◽  
Light Chain ◽  
Cultured Cells ◽  
Light Chains ◽  
Western Blots ◽  
Kinesin Light Chain ◽  
Heavy Chains ◽  
Carboxyl Terminal ◽  
Kinesin Molecule ◽  
Conventional Kinesin

Conventional kinesin is a motor protein implicated in the transport of a variety of cytoplasmic organelles along microtubules. The kinesin molecule consists of two heavy chains with motor domains at their amino termini and two light chains, which, together with the carboxyl termini of the heavy chains, are proposed to mediate binding to cargoes. Since the light chains are represented by multiple isoforms diverging at their carboxyl termini they are presumed to specify kinesin targeting to organelles. Previously, we isolated five cDNAs, encoding hamster kinesin light chain isoforms, and found that one of them (B or C) preferentially associated with mitochondria. To obtain additional evidence proving the specific location of various kinesin light chain isoforms on organelles, we made an antibody against a 56 amino-acid sequence found at the carboxyl-terminal regions of the hamster D and E isoforms. By indirect immunofluorescence, this antibody specifically labeled the Golgi complex in cultured cells. In western blots of total cell homogenates, it recognized two close polypeptides, one of which co-purified with the Golgi membranes. Thus, the results of this and previous studies demonstrate that different kinesin light chains are associated with different organelles in cells.

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