Paul B. Lazarow

Bio: Paul B. Lazarow is an academic researcher from Rockefeller University. The author has contributed to research in topics: Peroxisome & Microbody. The author has an hindex of 27, co-authored 41 publications receiving 4043 citations.

A fatty acyl-CoA oxidizing system in rat liver peroxisomes; enhancement by clofibrate, a hypolipidemic drug.

Abstract: Purified rat liver peroxisomes contain a cyanide-insensitive fatty acyl-CoA oxidizing system that uses O2 and NAD as electron acceptors. The system was detected by the ability of added palmitoyl-CoA to elicit O2 consumption, H2O2 production, and O2-dependent NAD reduction. The activity of this system is increased approximately one order of magnitude in rats treated with clofibrate, a hypolipidemic drug known to cause peroxisomal proliferation.

Peroxisomal membrane ghosts in Zellweger syndrome--aberrant organelle assembly.

Abstract: Peroxisomes are apparently missing in Zellweger syndrome; nevertheless, some of the integral membrane proteins of the organelle are present. Their distribution was studied by immunofluorescence microscopy. In control fibroblasts, peroxisomes appeared as small dots. In Zellweger fibroblasts, the peroxisomal membrane proteins were located in unusual empty membrane structures of larger size. These results suggest that the primary defect in this disease may be in the mechanism for import of matrix proteins.

Three hypolipidemic drugs increase hepatic palmitoyl-coenzyme A oxidation in the rat.

Abstract: Male rats treated with clofibrate, tibric acid, or Wy-14,643 show an 11- to 18-fold increase in the capacity of their livers to oxidize palmitoyl-coenzyme A. This provides a plausible biochemical mechanism for the action of these hypolipidemic drugs in reducing lipid concentrations in the serum.

THE SYNTHESIS AND TURNOVER OF RAT LIVER PEROXISOMES: I. Fractionation of Peroxisome Proteins

Abstract: Rat liver peroxisomes isolated by density gradient centrifugation were disrupted at pH 9, and subdivided into a soluble fraction containing 90% of their total proteins and virtually all of their catalase, D-amino acid oxidase, L-α-hydroxy acid oxidase and isocitrate dehydrogenase activities, and a core fraction containing urate oxidase and 10% of the total proteins. The soluble proteins were chromatographed on Sephadex G-200, diethylaminoethyl (DEAE)-cellulose, hydroxylapatite, and sulfoethyl (SE)-Sephadex. None of these methods provided complete separation of the protein components, but these could be distributed into peaks in which the specific activities of different enzymes were substantially increased. Catalase, D-amino acid oxidase, and L-α-hydroxy acid oxidase contribute a maximum of 16, 2, and 4%, respectively, of the protein of the peroxisome. The contribution of isocitrate dehydrogenase could be as much as 25%, but is probably much less. After dissolution of the cores at pH 11 , no separation between their urate oxidase activity and their protein was achieved by Sephadex G-200 chromatography.

Synthesis of a major integral membrane polypeptide of rat liver peroxisomes on free polysomes

Abstract: The manner of synthesis and assembly of the peroxisomal membrane proteins is unknown. Understanding these processes is essential to an understanding of the formation of the organelle. We have investigated the biogenesis of the previously identified major 21.7-kDa integral peroxisomal membrane polypeptide [Fujiki, Y., Fowler, S., Shio, H., Hubbard, A. L. & Lazarow, P. B. (1982) J. Cell Biol. 93, 103-110]. This protein was purified to apparent homogeneity and used to elicit a rabbit antiserum. In immunoblotting analysis, antibody bound only to the 22-kDa membrane polypeptide present exclusively in peroxisomal membranes. Total rat liver RNA was translated in a nuclease-treated rabbit reticulocyte cell-free protein-synthesizing system. The in vitro translation product, isolated by means of the antibody and Staphylococcus aureus cells, comigrated with the mature 22-kDa polypeptide in NaDodSO4/PAGE. Analysis of the translation products of RNAs from free and membrane-bound polysomes indicated that the mRNA for the 22-kDa membrane polypeptide is found predominantly in free polysomes. The results imply post-translational insertion of the membrane polypeptide into the peroxisomal membrane without proteolytic processing and suggest that peroxisomes, like mitochondria and chloroplasts, form by fission from preexisting organelles.

Lactate metabolism: a new paradigm for the third millennium

Abstract: For much of the 20th century, lactate was largely considered a dead-end waste product of glycolysis due to hypoxia, the primary cause of the O2 debt following exercise, a major cause of muscle fatigue, and a key factor in acidosis-induced tissue damage. Since the 1970s, a ‘lactate revolution’ has occurred. At present, we are in the midst of a lactate shuttle era; the lactate paradigm has shifted. It now appears that increased lactate production and concentration as a result of anoxia or dysoxia are often the exception rather than the rule. Lactic acidosis is being re-evaluated as a factor in muscle fatigue. Lactate is an important intermediate in the process of wound repair and regeneration. The origin of elevated [lactate] in injury and sepsis is being re-investigated. There is essentially unanimous experimental support for a cell-to-cell lactate shuttle, along with mounting evidence for astrocyte–neuron, lactate–alanine, peroxisomal and spermatogenic lactate shuttles. The bulk of the evidence suggests that lactate is an important intermediary in numerous metabolic processes, a particularly mobile fuel for aerobic metabolism, and perhaps a mediator of redox state among various compartments both within and between cells. Lactate can no longer be considered the usual suspect for metabolic ‘crimes’, but is instead a central player in cellular, regional and whole body metabolism. Overall, the cell-to-cell lactate shuttle has expanded far beyond its initial conception as an explanation for lactate metabolism during muscle contractions and exercise to now subsume all of the other shuttles as a grand description of the role(s) of lactate in numerous metabolic processes and pathways.

Putative X-linked adrenoleukodystrophy gene shares unexpected homology with ABC transporters

Abstract: Adrenoleukodystrophy (ALD) is an X-linked disease affecting 1/20,000 males either as cerebral ALD in childhood or as adrenomyeloneuropathy (AMN) in adults. Childhood ALD is the more severe form, with onset of neurological symptoms between 5-12 years of age. Central nervous system demyelination progresses rapidly and death occurs within a few years. AMN is a milder form of the disease with onset at 15-30 years of age and a more progressive course. Adrenal insufficiency (Addison's disease) may remain the only clinical manifestation of ALD. The principal biochemical abnormality of ALD is the accumulation of very-long-chain fatty acids (VLCFA) because of impaired beta-oxidation in peroxisomes. The normal oxidation of VLCFA-CoA in patients' fibroblasts suggested that the gene coding for the VLCFA-CoA synthetase could be a candidate gene for ALD. Here we use positional cloning to identify a gene partially deleted in 6 of 85 independent patients with ALD. In familial cases, the deletions segregated with the disease. An identical deletion was detected in two brothers presenting with different clinical ALD phenotypes. Candidate exons were identified by computer analysis of genomic sequences and used to isolate complementary DNAs by exon connection and screening of cDNA libraries. The deduced protein sequence shows significant sequence identity to a peroxisomal membrane protein of M(r) 70K that is involved in peroxisome biogenesis and belongs to the 'ATP-binding cassette' superfamily of transporters.

A conserved tripeptide sorts proteins to peroxisomes.

Abstract: The firefly luciferase protein contains a peroxisomal targeting signal at its extreme COOH terminus (Gould et al., 1987). Site-directed mutagenesis of the luciferase gene reveals that this peroxisomal targeting signal consists of the COOH-terminal three amino acids of the protein, serine-lysine-leucine. When this tripeptide is appended to the COOH terminus of a cytosolic protein (chloramphenicol acetyltransferase), it is sufficient to direct the fusion protein into peroxisomes. Additional mutagenesis experiments reveal that only a limited number of conservative changes can be made in this tripeptide targeting signal without abolishing its activity. These results indicate that peroxisomal protein import, unlike other types of transmembrane translocation, is dependent upon a conserved amino acid sequence.

A fatty acyl-CoA oxidizing system in rat liver peroxisomes; enhancement by clofibrate, a hypolipidemic drug.

Abstract: Purified rat liver peroxisomes contain a cyanide-insensitive fatty acyl-CoA oxidizing system that uses O2 and NAD as electron acceptors. The system was detected by the ability of added palmitoyl-CoA to elicit O2 consumption, H2O2 production, and O2-dependent NAD reduction. The activity of this system is increased approximately one order of magnitude in rats treated with clofibrate, a hypolipidemic drug known to cause peroxisomal proliferation.