Dataset Information

CDNA cloning of a liver isoform of the phosphorylase kinase alpha subunit and mapping of the gene to Xp22.2-p22.1, the region of human X-linked liver glycogenosis.

ABSTRACT: We have cloned cDNA molecules encoding another isoform of the alpha subunit of phosphorylase kinase (ATP:phosphorylase-b phosphotransferase, EC 2.7.1.38). Sequence comparison with the previously characterized muscle isoform reveals a pattern of highly conserved and variable domains and demonstrates that the isoforms are the products of distinct genes. In contrast to the muscle isoform gene, PHKA1, the gene of this additional isoform, PHKA2, is predominantly expressed in liver and other nonmuscle tissues. It was mapped to the distal short arm of the human X chromosome (Xp22.2-p22.1), the same region to which human X-linked liver glycogenosis due to phosphorylase kinase deficiency has been mapped. Thus, X-linked liver glycogenosis is probably caused by mutations affecting PHKA2.

SUBMITTER: Davidson JJ

PROVIDER: S-EPMC48603 | biostudies-other | 1992 Mar

REPOSITORIES: biostudies-other

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cDNA cloning of a liver isoform of the phosphorylase kinase alpha subunit and mapping of the gene to Xp22.2-p22.1, the region of human X-linked liver glycogenosis.

Davidson J J JJ Ozçelik T T Hamacher C C Willems P J PJ Francke U U Kilimann M W MW

Proceedings of the National Academy of Sciences of the United States of America 19920301 6

We have cloned cDNA molecules encoding another isoform of the alpha subunit of phosphorylase kinase (ATP:phosphorylase-b phosphotransferase, EC 2.7.1.38). Sequence comparison with the previously characterized muscle isoform reveals a pattern of highly conserved and variable domains and demonstrates that the isoforms are the products of distinct genes. In contrast to the muscle isoform gene, PHKA1, the gene of this additional isoform, PHKA2, is predominantly expressed in liver and other nonmuscle ...[more]

PMID: 1372435

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Project description:Fatal congenital nonlysosomal cardiac glycogenosis has been attributed to a subtype of phosphorylase kinase deficiency, but the underlying genes and mutations have not been identified. Analyzing four sporadic, unrelated patients, we found no mutations either in the eight genes encoding phosphorylase kinase subunits or in the two genes encoding the muscle and brain isoforms of glycogen phosphorylase. However, in three of five patients, we identified identical heterozygous R531Q missense mutations of the PRKAG2 gene, which encodes the gamma 2-subunit of AMP-activated protein kinase, a key regulator of energy balance. Biochemical characterization of the recombinant R531Q mutant protein showed >100-fold reduction of binding affinities for the regulatory nucleotides AMP and ATP but an enhanced basal activity and increased phosphorylation of the alpha -subunit. Other PRKAG2 missense mutations were previously identified in patients with autosomal dominant hypertrophic cardiomyopathy with Wolff-Parkinson-White syndrome, characterized by juvenile-to-adult clinical onset, moderate cardiac glycogenosis, disturbed excitation conduction, risk of sudden cardiac death in midlife, and molecular perturbations that are similar to--but less severe than--those observed for the R531Q mutation. Thus, recurrent heterozygous R531Q missense mutations in PRKAG2 give rise to a massive nonlysosomal cardiac glycogenosis of fetal symptomatic onset and rapidly fatal course, constituting a genotypically and clinically distinct variant of hypertrophic cardiomyopathy with Wolff-Parkinson-White syndrome. R531Q and other PRKAG2 mutations enhance the basal activity and alpha -subunit phosphorylation of AMP-activated protein kinase, explaining the dominant nature of PRKAG2 disease mutations. Since not all cases displayed PRKAG2 mutations, fatal congenital nonlysosomal cardiac glycogenosis seems to be genetically heterogeneous. However, the existence of a heart-specific primary phosphorylase kinase deficiency is questionable, because no phosphorylase kinase mutations were found.

Dataset Information

CDNA cloning of a liver isoform of the phosphorylase kinase alpha subunit and mapping of the gene to Xp22.2-p22.1, the region of human X-linked liver glycogenosis.

Publications

cDNA cloning of a liver isoform of the phosphorylase kinase alpha subunit and mapping of the gene to Xp22.2-p22.1, the region of human X-linked liver glycogenosis.

Similar Datasets

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