Mistargeting of peroxisomal L-alanine:glyoxylate aminotransferase to mitochondria in primary hyperoxaluria patients depends upon activation of a cryptic mitochondrial targeting sequence by a point mutation.

Purdue, P. Edward; Allsop, Jennifer; Isaya, Grazia; Rosenberg, L E; Danpure, Christopher J.

doi:10.1073/pnas.88.23.10900

Cited by 102 publications

(80 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The monogenic causes of NL/NC reported in the literature are very heterogeneous (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). This heterogeneity is evident in our cohort, in which causative mutations were distributed among 14 of the 30 genes screened.…”

Section: Discussionmentioning

confidence: 99%

Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis

Braun¹,

Lawson²,

Gee

et al. 2016

Clinical Journal of the American Society of Nephrology

117

110

View full text Add to dashboard Cite

Background and objectives Nephrolithiasis is a prevalent condition that affects 10%-15% of adults in their lifetime. It is associated with high morbidity due to colicky pain, the necessity for surgical intervention, and sometimes progression to CKD. In recent years, multiple monogenic causes of nephrolithiasis and nephrocalcinosis have been identified. However, the prevalence of each monogenic gene in a pediatric renal stone cohort has not yet been extensively studied.Design, setting, participants, & measurements To determine the percentage of cases that can be explained molecularly by mutations in one of 30 known nephrolithiasis/nephrocalcinosis genes, we conducted a high-throughput exon sequencing analysis in an international cohort of 143 individuals ,18 years of age, with nephrolithiasis (n=123) or isolated nephrocalcinosis (n=20). Over 7 months, all eligible individuals at three renal stone clinics in the United States and Europe were approached for study participation.Results We detected likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 16.8% (24 of 143) of affected individuals; 12 of the 27 detected mutations were not previously described as disease causing (44.4%). We observed that in our cohort all individuals with infantile manifestation of nephrolithiasis or nephrocalcinosis had causative mutations in recessive rather than dominant monogenic genes. In individuals who manifested later in life, causative mutations in dominant genes were more frequent. ConclusionsWe present the first exclusively pediatric cohort examined for monogenic causes of nephrolithiasis/ nephrocalcinosis, and suggest that important therapeutic and preventative measures may result from mutational analysis in individuals with early manifestation of nephrolithiasis or nephrocalcinosis.

show abstract

Section: Discussionmentioning

confidence: 99%

Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis

Braun¹,

Lawson²,

Gee

et al. 2016

Clinical Journal of the American Society of Nephrology

117

110

View full text Add to dashboard Cite

show abstract

“…AGT is normally peroxisomal in human liver, but in a subset of primary hyperoxaluria type 1 patients it is mistargeted to mitochondria (2). Although the molecular basis of the peroxisome-to-mitochondrion mistargeting of AGT in primary hyperoxaluria type 1 has been subjected to extensive investigation (3)(4)(5)(6), its normal targeting to peroxisomes has received much less attention (7,8).…”

mentioning

confidence: 99%

Peroxisomal Import of Human Alanine:glyoxylate Aminotransferase Requires Ancillary Targeting Information Remote from Its C Terminus

Huber

Birdsey

Lumb

et al. 2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

Although human alanine:glyoxylate aminotransferase (AGT) is imported into peroxisomes by a Pex5p-dependent pathway, the properties of its C-terminal tripeptide (KKL) are unlike those of any other type 1 peroxisomal targeting sequence (PTS1). We have previously suggested that AGT might possess ancillary targeting information that enables its unusual PTS1 to work. In this study, we have attempted to locate this information and to determine whether or not it is a characteristic of all vertebrate AGTs. Using the two-hybrid system, we show that human AGT interacts with human Pex5p in mammalian cells, but not yeast cells. Using (immuno)fluorescence microscopic analysis of the distribution of various constructs expressed in COS cells, we show the following. 1) The putative ancillary peroxisomal targeting information (PTS1A) in human AGT is located entirely within the smaller C-terminal structural domain of 110 amino acids, with the sequence between Val-324 and Ile-345 being the most likely candidate region. 2) The PTS1A is present in all mammalian AGTs studied (human, rat, guinea pig, rabbit, and cat), but not amphibian AGT (Xenopus). 3) The PTS1A is necessary for peroxisomal import of human, rabbit, and cat AGTs, but not rat and guinea pig AGTs. We speculate that the internal PTS1A of human AGT works in concert with the C-terminal PTS1 by interacting with Pex5p indirectly with the aid of a yet-to-be-identified mammal-specific adaptor molecule. This interaction might reshape the tetratricopeptide repeat domain allosterically, enabling it to accept KKL as a functional PTS1.Alanine:glyoxylate aminotransferase (AGT, 1 EC 2.6.1.44) catalyzes the transamination of the intermediary metabolite glyoxylate to glycine. A deficiency of AGT, as occurs in the hereditary disease primary hyperoxaluria type 1, allows glyoxylate to be oxidized to oxalate instead. The resulting increased synthesis and excretion of oxalate leads to the deposition of insoluble calcium oxalate in the kidney and urinary tract and, ultimately, renal failure (1). AGT is normally peroxisomal in human liver, but in a subset of primary hyperoxaluria type 1 patients it is mistargeted to mitochondria (2). Although the molecular basis of the peroxisome-to-mitochondrion mistargeting of AGT in primary hyperoxaluria type 1 has been subjected to extensive investigation (3-6), its normal targeting to peroxisomes has received much less attention (7,8).Peroxisomal import of human AGT is dependent on the presence of the type 1 peroxisomal targeting sequence (PTS1) receptor Pex5p, but not the PTS2 receptor Pex7p (7). However, several features of the peroxisomal targeting of AGT are unusual when compared with the targeting of other peroxisomal proteins. The C-terminal tripeptide of human AGT is KKL (9), which has a two-out-of-three match with the prototypical consensus PTS1 of (S/A/C)(K/R/H)(L/M) (10, 11). KKL is necessary for peroxisomal targeting of human AGT but insufficient to direct the peroxisomal targeting of reporter proteins, such as bacterial chloramphenicol acetyl...

show abstract

“…The minor allele itself appears to have a particularly complex phenotype; studies suggest that it has reduced catalytic activity (5,8) and reduced stability (5,7) and that the P11L mutation generates a cryptic mitochondrial targeting signal that affects protein trafficking (4,10,11). Although the trafficking differences between the major and minor allele proteins are well established (2), there is only indirect evidence supporting that the minor allele is destabilized, and some of these experiments are difficult to interpret because they assessed the minor allele in combination with other mutations or characterized proteins containing only one of the two minor allele mutations.…”

mentioning

confidence: 99%

In Vivo and in Vitro Examination of Stability of Primary Hyperoxaluria-associated Human Alanine:Glyoxylate Aminotransferase

Hopper

Pittman

Fitzgerald

et al. 2008

Journal of Biological Chemistry

View full text Add to dashboard Cite

Primary hyperoxaluria type I is a severe kidney stone disease caused by mutations in the protein alanine:glyoxylate aminotransferase (AGT). Many patients have mutations in AGT that are not deleterious alone but act synergistically with a common minor allele polymorphic variant to impair protein folding, dimerization, or localization. Although studies suggest that the minor allele variant itself is destabilized, no direct stability studies have been carried out. In this report, we analyze AGT function and stability using three approaches. First, we describe a yeast complementation growth assay for AGT, in which we show that human AGT can substitute for function of yeast Agx1 and that mutations associated with disease in humans show reduced growth in yeast. The reduced growth of minor allele mutants reflects reduced protein levels, indicating that these proteins are less stable than wild-type AGT in yeast. We further examine stability of AGT alleles in vitro using two direct methods, a mass spectrometry-based technique (stability of unpurified proteins from rates of H/D exchange) and differential scanning fluorimetry. We also examine the effect of known ligands pyridoxal 5-phosphate and aminooxyacetic acid on stability. Our work establishes that the minor allele is destabilized and that pyridoxal 5-phosphate and aminooxyacetic acid binding significantly stabilizes both alleles. To our knowledge, this is the first work that directly measures relative stabilities of AGT variants and ligand complexes. Because previous studies suggest that stabilizing compounds (i.e. pharmacological chaperones) may be effective for treatment of primary hyperoxaluria, we propose that the methods described here can be used in high throughput screens for compounds that stabilize AGT mutants.Deficiencies in the enzyme alanine:glyoxylate aminotransferase (AGT) 3 cause primary hyperoxaluria type I (PH1), a severe autosomal recessive kidney stone disease (1, 2). In humans, AGT is responsible for conversion of glyoxylate to glycine in the liver. Without functional AGT, glyoxylate builds up and is converted to calcium oxalate, which is deposited in the kidneys and can lead to kidney stones and renal failure. In many patients, deficiency of AGT results from one or two amino acid changes that decrease the stability of this enzyme. As a result, AGT may be degraded, become improperly localized, or form nonfunctional aggregates (1, 2).Over 50 different mutations of AGT and two polymorphic variants have been identified (1, 3). The two allelic forms consist of a "wild-type" major allele, AGTma, and a minor allele, AGTmi. The minor allele is present in ϳ20% of European and North American populations and contains P11L and I340M substitutions in the amino acid sequence and a 74-bp duplication in intron 1 (4, 5). The P11L and I340M substitutions, particularly P11L, have several biochemical effects, including decreasing catalytic activity and slowing the dimerization rate, but by themselves are not disease-causing (4, 5). The minor allele of AGT is delete...

show abstract

Mistargeting of peroxisomal L-alanine:glyoxylate aminotransferase to mitochondria in primary hyperoxaluria patients depends upon activation of a cryptic mitochondrial targeting sequence by a point mutation.

Cited by 102 publications

References 18 publications

Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis

Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis

Peroxisomal Import of Human Alanine:glyoxylate Aminotransferase Requires Ancillary Targeting Information Remote from Its C Terminus

In Vivo and in Vitro Examination of Stability of Primary Hyperoxaluria-associated Human Alanine:Glyoxylate Aminotransferase

Contact Info

Product

Resources

About