Vitamin K-dependent gamma-glutamyl carboxylase activity in the chick embryonic chorioallantoic membrane

Proteomic Analysis of Chicken Chorioallantoic Membrane (CAM) during Embryonic Development Provides Functional Insight

In oviparous animals, the egg contains all resources required for embryonic development. The chorioallantoic membrane (CAM) is a placenta-like structure produced by the embryo for acid-base balance, respiration, and calcium solubilization from the eggshell for bone mineralization. The CAM is a valuable in vivo model in cancer research for development of drug delivery systems and has been used to study tissue grafts, tumor metastasis, toxicology, angiogenesis, and assessment of bacterial invasion. However, the protein constituents involved in different CAM functions are poorly understood. Therefore, we have characterized the CAM proteome at two stages of development (ED12 and ED19) and assessed the contribution of the embryonic blood serum (EBS) proteome to identify CAM-unique proteins. LC/MS/MS-based proteomics allowed the identification of 1470, 1445, and 791 proteins in CAM (ED12), CAM (ED19), and EBS, respectively. In total, 1796 unique proteins were identified. Of these, 175 (ED12), 177 (ED19), and 105 (EBS) were specific to these stages/compartments. This study attributed specific CAM protein constituents to functions such as calcium ion transport, gas exchange, vasculature development, and chemical protection against invading pathogens. Defining the complex nature of the CAM proteome provides a crucial basis to expand its biomedical applications for pharmaceutical and cancer research.

New Aspects of Vitamin K Research with Synthetic Ligands: Transcriptional Activity via SXR and Neural Differentiation Activity

Vitamin K is classified into three homologs depending on the side-chain structure, with 2-methyl-1,4-naphthoqumone as the basic skeleton. These homologs are vitamin K₁ (phylloquinone: PK), derived from plants with a phythyl side chain; vitamin K₂ (menaquinone-n: MK-n), derived from intestinal bacteria with an isoprene side chain; and vitamin K₃ (menadione: MD), a synthetic product without a side chain. Vitamin K homologs have physiological effects, including in blood coagulation and in osteogenic activity via γ-glutamyl carboxylase and are used clinically. Recent studies have revealed that vitamin K homologs are converted to MK-4 by the UbiA prenyltransferase domain-containing protein 1 (UBIAD1) in vivo and accumulate in all tissues. Although vitamin K is considered to have important physiological effects, its precise activities and mechanisms largely remain unclear. Recent research on vitamin K has suggested various new roles, such as transcriptional activity as an agonist of steroid and xenobiotic nuclear receptor and differentiation-inducing activity in neural stem cells. In this review, we describe synthetic ligands based on vitamin K and exhibit that the strength of biological activity can be controlled by modification of the side chain part.

The chick chorioallantoic membrane: a model of molecular, structural, and functional adaptation to transepithelial ion transport and barrier function during embryonic development

The chick chorioallantoic membrane is a very simple extraembryonic membrane which serves multiple functions during embryo development; it is the site of exchange of respiratory gases, calcium transport from the eggshell, acid-base homeostasis in the embryo, and ion and H(2)O reabsorption from the allantoic fluid. All these functions are accomplished by its epithelia, the chorionic and the allantoic epithelium, by differentiation of a wide range of structural and molecular peculiarities which make them highly specialized, ion transporting epithelia. Studying the different aspects of such a developmental strategy emphasizes the functional potential of the epithelium and offers an excellent model system to gain insights into questions partly still unresolved.

Calcium uptake by chorioallantoic membrane: effects of vitamins D and K

The chorioallantoic membrane (CAM) of birds is an epithelial tissue that actively transports large amounts of Ca during embryonic development. In this study the effect of vitamins D and K on Ca uptake by the CAM was studied. Four dietary treatments were used to produce eggs that are the following: deficient in vitamins D and K (-D/-K), sufficient in both (+D/+K), or deficient in one and sufficient in the other (-D/+K or +D/-K). Vitamin D-deficient (-D) Japanese quail embryos (from hens fed 1,25-dihydroxyvitamin D3) do not hatch because of severe Ca deficiency resulting from their inability to obtain Ca from shell, whereas vitamin K deficiency results in only 14% reduction in hatchability. The results demonstrate that Ca uptake by CAM is vitamin D dependent and only slightly vitamin K dependent. Ca-binding activity of CAM extracts was unchanged by vitamin K deficiency, and only a small increase was provided by vitamin D treatment. Vitamin D stimulated both Ca entry and exist from the chorion cells as indicated by the increased accumulated 45Ca in +D embryos. We conclude that vitamin D is essential for the utilization of eggshell Ca by the developing embryo and hence its survival, suggesting that Ca transport across the CAM is largely a vitamin D-dependent process.

Transepithelial calcium transport in the chick chorioallantoic membrane. I. Isolation and characterization of chorionic ectoderm cells

The chicken eggshell supplies approximately 80% of the calcium found in the hatchling chick. The mobilization of eggshell calcium into the developing embryo involves the transepithelial transport of large amounts of calcium in a development-specific manner. The cells responsible for the transport of eggshell calcium into the embryonic circulation are the ectodermal cells of the chorioallantoic membrane. In this report, we present a method for the isolation and culture of chorioallantoic membrane ectodermal cells, which are amenable to direct experimental manipulation. Cell preparations are characterized with respect to the expression of an ectoderm-specific cell surface marker (transcalcin, a calcium-binding protein), and a specific enzymatic activity (elevated Ca(2+)-activated ATPase). Functional assessment of in vitro cellular calcium uptake by 45Ca2+ tracer kinetics indicates the persistence of a temperature-sensitive, rapid-influx pathway similar to that observed in vivo. The preparations of primary ectodermal cells present an in vitro system applicable to the experimental analysis of calcium metabolism and transport by the chick chorioallantoic membrane.

Identification and characterization of a calcium-binding protein from human placenta

The human placenta has been found to contain a specific calcium-binding protein (HCaBP) which increases in amount as a function of gestation. A procedure is described for the purification of the HCaBP to chromatographic and electrophoretic homogeneity. The HCaBP is (a) a high molecular weight protein with a native Mr of 150 000 and appears to be a dimer of subunits of Mr = 70 000; and (b) an acidic protein with a pI of 4.6. Amino acid analysis of the HCaBP revealed an abundance of acidic amino acid residues (27 per cent = Asp and Glu). A specific antiserum has been prepared against purified HCaBP. With Ouchterlony double immunodiffusion, the HCaBP appears to be specific for the human placenta, and is not cross-immunoreactive with the CaBP of the chick embryonic chorio-allantoic membrane.

The physiological effects of feeding warfarin poultry

A 20 week study using layer and broiler strain chicks of both sexes was undertaken to determine whether poultry were susceptible to warfarin-induced granulomatous endocardial lesions. Birds were fed a corn-soybean meal basal diet with no added vitamin K, supplemented with either 0, 25, 50, or 100 ppm of warfarin or vitamin K at .6 mg/kg of diet. Broiler chicks showed a higher incidence of hemorrhages, more mortality, and longer prothrombin times than did the layer strain fed the same diets. Regardless of the breed, female chicks fed the highest warfarin level had significantly longer prothrombin times than the male chicks. However, there were no sex differences associated with mortality or incidence of hemorrhages among birds fed the experimental diets. Growth was most significantly reduced for chicks fed the highest warfarin level and to a lesser degree for birds fed 50 ppm of warfarin. In contrast to the first 10 weeks of the study, there was a sharp decline in mortality, incidence of hemorrhages, and prothrombin times during the last 10 weeks of the study. Layer and broiler strains of chickens fed warfarin for 20 weeks showed no evidence of granulomatous endocardial lesions as was reported for swine (Oshiro and Brooks, 1975).

Gamma-carboxyglutamic acid

Gamma-carboxyglutamic acid is an amino acid with a dicarboxylic acid side chain. This amino acid, with unique metal binding properties, confers metal binding character to the proteins into which it is incorporated. This amino acid has been discovered in blood coagulation proteins (prothrombin, Factor X, Factor IX, and Factor VII), plasma proteins of unknown function (Protein C, Protein S, and Protein Z), and proteins from calcified tissue (osteocalcin and bone-Gla protein). It has also been observed in renal calculi, atherosclerotic plaque, and the egg chorioallantoic membrane, among other tissues. Gamma-carboxyglutamic acid is synthesized by the post-translational modification of glutamic acid residues. This reaction, catalyzed by a hepatic carboxylase, requires reduced vitamin K, oxygen, and carbon dioxide. The function of gamma-carboxyglutamic acid is uncertain. In prothrombin gamma-carboxyglutamic acid residues bound to metal ions participate as an intramolecular non-covalent bridge to maintain protein conformation. Additionally, these amino acids participate in the calcium-dependent molecular assembly of proteins on membrane surfaces through intermolecular bridges involving gamma-carboxyglutamic acid and metal ions.

Post-translational carboxylation of preprothrombin

In summary, in this review on the function of vitamin K in post-translational modification of precursor proteins by carboxylation of certain glutamyl residues, I have tried to cover in particular the recent work on the reaction, the enzymes involved and the mechanisms being considered. In doing this I have also considered vitamin K, its discovery, its functional form and the possible relation of its metabolism to the carboxylation reaction. Equally the various vitamin K-dependent gla-containing proteins currently known have been described. The carboxylation of synthetic small molecule exogenous substrates and the synthesis and metabolism of the products of carboxylation are of great help in studying the reaction. Structural specificity of vitamin K analogs in vivo and in vitro has been compared and the use of various antagonists in vivo and in vitro considered in attempts to gain an understanding of the overall reaction. The reactions subsequent to carboxylation, e.g., the activation of prothrombin to thrombin via serine proteases and the related activation of the other vitamin K-dependent proteins have not been considered in this review. The review has not covered prothrombin or other vitamin K-dependent protein isolation, nor the determination of these proteins. As the vitamin K-dependent protein carboxylation story has developed over the past six years, a number of reviews have been written which help in keeping up with the various aspects of the field as it has expanded. These reviews refer to many of the papers I have had to eliminate due to space limitations. They are referenced as 469-489. The review is in no sense comprehensive and many papers have been missed or only mentioned. I have tried to concentrate on the more recent work and, thus, much of the very fine work of the 1940's on vitamin K chemistry is hardly mentioned. Some redundancy has been built into the organization of the review so that a reader can obtain a reasonable view of any one section without having to search the whole review for all possible relevant information on any particular part of the field.

Vitamin K-dependent gamma-carboxyglutamic acid formation by mouse renal adenocarcinoma cells (RAG)

Previous studies have identified gamma-carboxyglutamic acid as a constituent of one or more protein(s) synthesized by rat and chicken kidney microsomes in vitro in a vitamin K-dependent post-translational reaction [1]. Incubation of microsomes from a mouse kidney cell line (RAG) with [14C]NaHCO3 results in formation of protein-bound [14C]gamma-carboxylglutamic acid. Incorporation is stimulated threefold by addition of the active vitamin K compound 2-methyl, 3-farnesyl, 1,4-naphthoquinone. At least 90% of incorporated, nondialyzable [14C] is situated in the gamma-carboxyl group of gamma-carboxyglutamic acid residues.