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PubMed2004

Metabolic alteration of the N-glycan structure of a protein from patients with a heterozygous protein deficiency.

Glycosylation, an important post-translation modification, could alter biological activity or influence the clearance rates of glycoproteins. We report here the first example of a heterozygous protein deficiency leading to metabolic alteration of N-glycan structures in residual secreted protein. Analysis of C1 esterase inhibitor (C1INH) glycans from normal individuals and patients with hereditary deficiency of C1INH demonstrated identical O-glycan structures but the N-glycans of patients with a heterozygous genetic deficiency were small, highly charged and lacked sialidase releasable N-acetylneuraminic acid. Structural studies indicate that the charge character of these aberrant N-glycan structures may result from the presence of mannose-6-phosphate residues. These residues might facilitate secretion of C1INH through an alternate lysosomal pathway, possibly serving as a compensatory mechanism to enhance plasma levels of C1INH in these deficient patients.

Angioedema↗
PubMed2007

Heterozygous deletion of mitotic arrest-deficient protein 1 (MAD1) increases the incidence of tumors in mice.

Mitotic arrest-deficient protein 1 (MAD1) is a component of the mitotic spindle assembly checkpoint. We have created a knockout mouse model to examine the physiologic consequence of reduced MAD1 function. Mad1(+/-) mice were successfully generated, but repeated paired mating of Mad1(+/-) with Mad1(+/-) mice failed to produce a single Mad1(-/-) animal, suggesting that the latter genotype is embryonic lethal. In aging studies conducted for >18 months, Mad1(+/-) mice compared with control wild-type (wt) littermates showed a 2-fold higher incidence of constitutive tumors. Moreover, 42% of Mad1(+/-) (P < 0.03), but 0% of wt, mice developed neoplasia after treatment with vincristine, a microtubule depolymerization agent. Mad1(+/-) mouse embryonic fibroblasts (MEF) were found to be more prone than wt cells to become aneuploid; Mad1(+/-), but not wt, MEFs produced fibrosarcomas when explanted into nude mice. Our results indicate an essential MAD1 function in mouse development and correlate Mad1 haploinsufficiency with increased constitutive tumors.

Amino Acid Sequence↗
PubMed1996

Effect of maternal protein deficiency during pregnancy and lactation on the organic matrix composition of the bone and skin of the sucklings of rat.

Effect of a staple Nigerian diet comprising of cassava flour, vegetable soup and fish, and containing 10% protein on bone and skin organic matrix of the offspring of rats fed the diet during pregnancy and lactation was studied. Two types of the diet were formulated. One contained 10% protein for the poor and the other 21% protein for the rich Nigerians. The two types of diet were dried at 70 degrees C for 24 hrs and ground into powder so that the rat could consume it. Laboratory rat chow was used as the control diet and it contained 21% protein. Each diet was fed to different groups of rats with water ad libitum during gestation and lactation. Chemical composition of the bone and skin matrix of the sucklings of the rats at 10 and 21 days of age were determined. The weights of the femur, humerus and skin as well as nitrogen, hexosamine and uronic acid concentrations in the bone and skin, and calcium concentration in the bone of sucklings whose dams were fed the diet containing 10% protein were lower than those of sucklings of dams fed diet containing 21% protein. Proline:Nitrogen and Hydroxyproline:Nitrogen concentration ratios in the bone and skin, and Calcium:Nitrogen concentration ratio in the bone were not affected by the level of dietary protein given to the dams. The quantity and not the composition of organic matrix constituents, collagen and chondroitin sulphate were reduced by maternal protein deficiency. Improper formation of bone matrix caused reduced calcification. It is concluded that the 10% dietary protein eaten by poor Nigerians is inadequate to support normal bone and skin weight and matrix composition of sucklings from dams consuming the diet.

Animal Feed↗
PubMed1999

[Effect of protein deficiency in the female rat diet during pregnancy and lactation on the activity of the membrane and soluble forms of digestive enzymes in the offspring small intestine].

Protein deficiency in female rats diet during pregnancy and lactation resulted in deceleration of induction of sucrase both forms in the jejunum and ileum; in acceleration of induction of the maltase membrane from in the jejunum; and in suppression of the lactase membrane form in the ileum; in earlier forming of the adult-type distribution of activity of the membrane form of intestinal alkaline phosphatase and in a decrease in activity of the enzyme soluble form. The findings are corroborated by a suppression of activities of the membrane and soluble forms of the small intestine digestive enzymes in 30-day old rat pups fed with a control (adequate) ration starting 21 days after the birth.

Alkaline Phosphatase↗
PubMed1978

Immune response in malnutrition. Effect of protein deficiency on the DNA synthetic response to alloantigens.

To evaluate the DNA synthetic response to alloantigens by lymphocytes from mice fed diets with normal (27%) and low (8%) protein content, we quantitated the uptake of 125IUDR in spleens of lethally irradiated adult F1 hybrids injected with cells with parental C57BL/6 donors kept on either diet. Thymocytes, spleen and lymph node cells from protein-restricted parental mice synthesized higher amounts of DNA than those from normally fed controls. Added thymocytes from either malnourished or normal F1 hybrids had similar inhibitory effects on the response of an active parental inoculum. The results indicate that cells from mice kept on a moderately protein-deficient diet for 3--5 weeks after weaning, have increased capacity to proliferate in response to alloantigens, suggesting a high proportion of reactive cells and/or changes in the ratio of the interacting cell populations in their lymphoid organs.

DNA↗
PubMedDate not supplied

Lipofuscin formation in the developing nervous system of squirrel monkeys consequent to maternal dietary protein deficiency during gestation.

The formation of lipofuscin pigment under the extrinsic influence of maternal protein deprivation during most of the gestation period has been demonstrated in the cerebellum and motor cortex of the developing fetuses and neonates in squirrel monkeys. The controls maintained on high protein diets failed to show lipofuscin pigment in appreciable quantities. The dirty yellow to dark brown pigment bodies exist as homogeneous particulates as well as duplex structures, each with a thin, irregular, light brown cortex, studded with one or more darker granules, and a medulla filled with sharp yellow substance. The malnourished neonates, especially in the third and fifth laminae of motor cortex, show loose aggregations of lipofuscin bodies in the apical dendrite and occasionally in the body of the dendritic branches but not in the axon hillock or the body of the axon. Histochemically, the pigment is a complex of lipids, carbohydrates and proteins, showing strong reaction for non-specific esterase and acid phosphatase and mild activity of succinate and lactate dehydrogenase and monoamine oxidase, which puts the pigment observed in the same category as the typical aging pigment described in literature. It is clear that maternal protein deficiency during the critical period of the fetal brain development has an adverse effect on its biochemical maturation. The accumulation of lipofuscin pigment is probably one manifestation of the metabolic changes in the neurons, which may have the impact of hastening the aging process, if protein deprivation is continued into the postnatal period.

Aging↗
PubMed1992

[Ménétrier's disease--a rare cause of a protein deficiency syndrome].

Hypoproteinaemia (total proteins 5.2 g/dl) and hypoalbuminaemia (2.7 g/dl) were demonstrated in a 44-year-old woman with leg oedema during the previous four months and 10-kg weight gain during the previous year. A protein-losing enteropathy was diagnosed, all other causes having been excluded. Gastroscopy revealed giant hypertrophic gastritis. A biopsy showed foveolar hyperplasia with some inflammatory infiltrates, typical of Ménétrier's disease. Endosonography excluded any additional infiltrative process of the bowel wall. Long-term treatment with ranitidine, 150 g twice daily, achieved normalization of total protein and albumin concentrations. But the macroscopic changes in the gastric wall were still recognizable on repeat gastroscopy. As there is a danger of malignant degeneration gastroscopy and, if indicated, endosonography should be repeated annually.

Adult↗
PubMed2004

Impaired response of biliary lipid secretion to a lithogenic diet in phosphatidylcholine transfer protein-deficient mice.

Phosphatidylcholine transfer protein (PC-TP) is a cytosolic lipid transfer protein that is highly expressed in liver and catalyzes intermembrane transfer of phosphatidylcholines in vitro. To explore a role for PC-TP in the hepatocellular trafficking of biliary phosphatidylcholines, we characterized biliary lipid secretion using Pctp(-/-) and wild-type littermate control mice with C57BL/6J and FVB/NJ genetic backgrounds, which express PC-TP at relatively high and low levels in liver, respectively. Eight-week-old male Pctp(-/-) and wild-type mice were fed a chow diet or a lithogenic diet, which served to upregulate biliary lipid secretion. In chow-fed mice, the absence of PC-TP did not reduce biliary phospholipid secretion or alter the phospholipid composition of biles. However, the responses in secretion of biliary phospholipids, cholesterol, and bile salts to the lithogenic diet were impaired in Pctp(-/-) mice from both genetic backgrounds. Alterations in biliary lipid secretion could not be attributed to transcriptional regulation of the expression of canalicular membrane lipid transporters, but possibly to a defect in their trafficking to the canalicular membrane. These findings support a role for PC-TP in the response of biliary lipid secretion to a lithogenic diet, but not specifically in the hepatocellular transport and secretion of phosphatidylcholines.

Animals↗
PubMed1978

Limited tryptic digestion of human serum low-density lipoprotein: isolation and characterisation of the protein-deficient particle and of its apoprotein.

Limited tryptic digestion of human serum low-density (LD) lipoprotein (rho 1.024-1.045 g/ml) under defined conditions permitted isolation by gel filtration chromatography of a stable, protein-deficient lipoprotein; the liberated protein was separated as a mixture of peptides of low molecular weight (less than 5000). Comparison of the chemical, physical and immunological characteristics of the trypsin-treated LD-lipoprotein with those of the native preparation revealed several differences, including (a) a diminished protein content (loss of some 20-25% of the total protein of LD-lipoprotein) and increased proportions of the various lipid components, except for triglyceride (probably resulting from a loss of bound free fatty acids with the liberated peptides); (b) a greater heterogeneity in particle size and slightly larger mean diameter; (c) a lower hydrated density and greater peak sf rate than the native LD-lipoprotein (d) an increased net negative charge; and (e) a partial immunological identity between LD-lipoprotein and the corresponding trypsin-treated fraction. While the amino acid compositions of the protein moieties of LD-lipoprotein and of trypsin-treated LD-lipoprotein were essentially identical, trypsin-treated apo-LD-lipoprotein was distinct in its complete solubility in urea-containing buffers at high concentrations, and also in its partial solubility in buffers lacking denaturing agents. Comparison of the apoproteins of the native and trypsin-treated LD-lipoproteins by electrophoretic techniques based on molecular weight revealed a transformation of the high-molecular weight material (greater than 250 000) characteristic of apo-LD lipoprotein into several polypeptide species (10 major forms) ranging in size from 161 500 to about 10 000. The largest of these (band b1: 161 500) could be completely dissociated into smaller components (b2: 93 500 and b3: 77 000) upon extensive heat treatment at 90 degrees C. Electrophoresis of the soluble fraction of apo-LD-lipoprotein and of that from its trypsin-treated counterpart in polyacrylamide gels containing urea at basic pH showed the disappearance of the small amounts (less than 5%) of C apoproteins of apo-LD-lipoprotein upon tryptic treatment. These results, which were highly reproducible in LD-lipoprotein preparations from different individuals, suggest that trypsin-treated LD-lipoprotein may provide a model for investigation of the organisation and structural role of the prinicipal apoprotein (apolipoprotein-B) in the LD-lipoprotein molecule.

Amino Acids↗
PubMed1983

Differences in nitrogen metabolism between protein-deficient and energy-deficient rats with similarly restricted growth rates.

Paired groups of rats whose growth rates were restricted to similar degrees by feeding either protein- or energy-deficient diets had very different patterns of nitrogen metabolism. The protein-deficient animals showed evidence of dysadaptation in that liver protein was much more reduced than in the energy-deficient ones, whereas total muscle protein was higher. Plasma albumin concentrations decreased only in animals fed the low protein diet; with energy restriction a small but significant rise in albumin was seen. Although plasma amino acid concentration fell in both protein- and energy-restricted groups, a distorted pattern, with a markedly raised non-essential:essential amino acid ratio was found only in the protein-deficient rats. These differences in nitrogen metabolism could not be explained on the basis of variations in the plasma concentrations of insulin, corticosterone or growth hormone. The relationship of these changes to the development of kwashiorkor in man, and the use of plasma albumin and amino acid as indicators of inappropriate internal distribution of protein, resulting in dysadaptation, are discussed.

Amino Acids↗
PubMed1988

Interaction of alcohol and protein deficiency on rat brain synaptosomal (Na+-K+)-ATPase.

Administration of low amounts of ethanol for a prolonged period increases rat brain synaptosomal (Na+-K+)-ATPase activity, the increase being less in the protein deficient rats. The adaptive mechanism to offset the stress imposed by the continued presence of ethanol seems to be depressed by low plane of nutrition. In vivo and in vitro effects of ethanol on (Na+-K+)ATPase seems to be different.

Animals↗
PubMed1997

Adrenoleukodystrophy protein-deficient mice represent abnormality of very long chain fatty acid metabolism.

We have generated a line of mice deficient in adrenoleukodystrophy protein (ALDP) by gene targeting in order to clarify the pathophysiology of adrenoleukodystrophy (ALD). ALDP-deficient male and female mice appeared normal clinically at least up to 12 months. Western blot analysis showed the absence of ALDP in the brain, spinal cord, lung, and kidney and normal expression of PMP70 in the liver, lung, and kidney. The amounts of C26:0 increased by 73-240% in the brain, spinal cord, lung, and kidney. beta-Oxidation of very long chain fatty acids (VLCFA) in cultured hepatocytes and fibroblasts was reduced to 35-50% of normal. Light and electron microscopy did not show demyelination in the brain, spinal cord, and peripheral nerve. Thus, the deficiency of ALDP in mice impairs the peroxisomal fatty acid beta-oxidation but does not duplicate the clinical and pathological abnormalities of the human ALD. These observations suggest that the accumulation of VLCFA alone is not sufficient to cause demyelination in the nervous system.

ATP Binding Cassette Transporter, Subfamily D, Mem↗