<i>Xenopus</i> oocytes can synthesise but do not secrete the Z variant of human α<sub>1</sub>‐antitrypsin

Foreman, Richard C.; Judah, J. D.; Colman, Alan

doi:10.1016/0014-5793(84)80211-2

Cited by 58 publications

(26 citation statements)

References 22 publications

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“…alAT is present in the media of oocytes injected both with M and Z mRNA while no immunoprecipitable material could be detected in water-injected oocytes. This finding contrasts with an earlier report in which no oocyte secreted Z alAT could be detected [16]. The M , of the secreted alAT (58000) is similar to that observed for '251-labelled alAT isolated from human serum.…”

Section: Secrefion Of Al -Antitrypsincontrasting

confidence: 99%

Human α₁ ‐antitrypsin expression in Xenopus oocytes

Errington

Bathurst

Carrell

1985

European Journal of Biochemistry

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Injection of equivalent amounts of normal (PiMM) or abnormal (PiZZ) a,-antitrypsin mRNA into Xenopus oocytes resulted in secretion of both the normal and abnormal a,-antitrypsin. A much lower proportion of the abnormal protein was secreted, and the Z a,-antitrypsin that was not secreted accumulated within the cell in a high-mannose form. The time taken for secretion of the normal and abnormal proteins was identical. Both the secreted and intracellular a, -antitrypsin synthesized by oocytes were functionally active.x,-Antitrypsin (alAT) is a glycoprotein of M , 51 000, whose major physiological role is to inhibit elastase and cathepsin G released by leukocytes [l]. Some 1 in 2000 Northern Europeans are homozygous for the Z variant of %,AT, which differs from the normal, M, by a single base change G + A in the DNA sequence [2] and leads to an amino acid substitution Glu + Lys at position 342. The Z variant is associated with intrahepatic accumulation of alAT and a gross decrease in its plasma concentration. Clinically ZZ homozygotes are predisposed to premature emphysema, and there is also a significant occurrence of liver disease [3, 41. Studies of the half-life of circulating Z protein have excluded an increased rate of degradation as a cause of its low plasma level [5].Measurement of a,AT mRNA levels in the livers of individuals homozygous for M or Z a,AT has shown that Z %,AT mRNA is present at a similar level to that of M [6].Messenger RNA for Z alAT translates as efficiently as normal M in a cell-free system and in the presence of dog pancreas membranes, both polypeptides are sequestered with consequent cleavage of the N-terminal signal sequence and corc glycosylation [7, 81. These findings imply that the block in secretion of Z alAT occurs at a later point in the secretory Investigation of later processing steps and secretion can be accomplished by using a surrogate secretory system, such as the Xenopus oocyle. This large cell (up to 1.2 mm diameter) can efficiently translatc cxogenous mRNA, and subsequently process and secrete foreign secretory proteins (see review [9]).In this paper we have used Xenopus oocytes to compare the synthesis and secretion of M a,AT with the Z variant. pathway. MATERIALS AND METHODS Chemicals ~-[~'S]Methionine and endo-fl-N-acetylglucosaminidaseH were obtained from New England Nuclear (Waltham MA), oligo(dT)-cellulose (type 2) from Collaborative Research (Lexington MA); human ieukocyte elastase was a kind gift from Dr P. George, and rabbit anti-(human alAT) serum was from DAKO (Copenhagen). Human a,AT was purified as described in [I 01 and iodinated by the chloramine-T method [ill.Preparation of messenger RNA Human liver from individuals homozygous for M or Z xlAT was obtained as previously described [7] and stored at -80 C until used. RNA was isolated by phenol extraction [12, 131 and the poly(A)-containing RNA species purified by binding twice to oligo(dT)-cellulose without prior removal of DNA [7]. Prepnra t ioii and micro inject ion of oo cy tesXenopus oocytes were obtained...

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Section: Secrefion Of Al -Antitrypsincontrasting

confidence: 99%

Human α₁ ‐antitrypsin expression in Xenopus oocytes

Errington

Bathurst

Carrell

1985

European Journal of Biochemistry

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“…Technical limitations in biosynthetic labeling and analytical methods in several recent studies examining biosynthesis and secretion of a1PI (25,29) have prevented definitive identification of the mechanism accounting for low serum concentrations in deficient individuals. The results ofour study indicate that a1PI is synthesized and secreted byXenopus oocytes injected with PiZZ liver mRNA and by peripheral blood monocytes from PiZZ individuals but secretion occurs at a reduced rate when compared to that of PiMM a1PI.…”

Section: Discussionmentioning

confidence: 99%

The cellular defect in alpha 1-proteinase inhibitor (alpha 1-PI) deficiency is expressed in human monocytes and in Xenopus oocytes injected with human liver mRNA.

Perlmutter¹,

Kay²,

Cole³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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“…The mutant ␣1-ATZ protein is retained in the endoplasmic reticulum (ER) of liver cells rather than secreted into the blood and body fluids (5,6). Circulating blood levels of ␣1-AT in deficient patients reach 10 -15% of the levels present in the general population.…”

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confidence: 99%

A Naturally Occurring Nonpolymerogenic Mutant of α1-Antitrypsin Characterized by Prolonged Retention in the Endoplasmic Reticulum

Schmidt

Teckman

et al. 2001

Journal of Biological Chemistry

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The classical form of ␣1-antitrypsin (␣1-AT) deficiency is associated with a mutant ␣1-ATZ molecule that polymerizes in the endoplasmic reticulum (ER) of liver cells. A subgroup of individuals homozygous for the protease inhibitor (PI) Z allele develop chronic liver injury and are predisposed to hepatocellular carcinoma. In this study we evaluated the primary structure of ␣1-AT in a family in which three affected members had severe liver disease associated with ␣1-AT deficiency. We discovered that one sibling was a compound heterozygote with one PI Z allele and a second allele, the PI Z ؉ saar allele, bearing the mutation that characterizes ␣1-ATZ as well as the mutation that characterizes ␣1-AT Saarbrucken (␣1-AT saar). The mutation in PI saar introduces a premature termination codon resulting in an ␣1-AT protein truncated for 19 amino acids at its carboxyl terminus. Studies of a second sib with severe liver disease and other living family members did not reveal the presence of the ␣1-AT saar mutation and therefore do not substantiate a role for this mutation in the liver disease phenotype of this family. However, studies of ␣1-AT saar and ␣1-ATZ ؉ saar expressed in heterologous cells show that there is prolonged intracellular retention of these mutants even though they do not have polymerogenic properties. These results therefore have important implications for further understanding the fate of mutant ␣1-AT molecules, the mechanism of ER retention, and the pathogenesis of liver injury in ␣1-AT deficiency.

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Xenopus oocytes can synthesise but do not secrete the Z variant of human α₁‐antitrypsin

Cited by 58 publications

References 22 publications

Human α₁ ‐antitrypsin expression in Xenopus oocytes

Human α₁ ‐antitrypsin expression in Xenopus oocytes

The cellular defect in alpha 1-proteinase inhibitor (alpha 1-PI) deficiency is expressed in human monocytes and in Xenopus oocytes injected with human liver mRNA.

A Naturally Occurring Nonpolymerogenic Mutant of α1-Antitrypsin Characterized by Prolonged Retention in the Endoplasmic Reticulum

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Xenopus oocytes can synthesise but do not secrete the Z variant of human α1‐antitrypsin

Cited by 58 publications

References 22 publications

Human α1 ‐antitrypsin expression in Xenopus oocytes

Human α1 ‐antitrypsin expression in Xenopus oocytes

The cellular defect in alpha 1-proteinase inhibitor (alpha 1-PI) deficiency is expressed in human monocytes and in Xenopus oocytes injected with human liver mRNA.

A Naturally Occurring Nonpolymerogenic Mutant of α1-Antitrypsin Characterized by Prolonged Retention in the Endoplasmic Reticulum

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Xenopus oocytes can synthesise but do not secrete the Z variant of human α₁‐antitrypsin

Human α₁ ‐antitrypsin expression in Xenopus oocytes

Human α₁ ‐antitrypsin expression in Xenopus oocytes