Novel Peroxisomal Populations in Subcellular Fractions from Rat Liver

Abstract

According to current concepts, new peroxisomes are formed by division of pre-existing peroxisomes or by budding from a peroxisomal reticulum. Recent cytochemical and biochemical data indicate that protein content in peroxisomes are heterogenous and that import of newly synthesized proteins may be restricted to certain protein import-competent peroxisomal subcompartments (Yamamoto, K., and Fahimi, H. D. (1987) J. Cell Biol. 105, 713-722; Heinemann, P., and Just, W. W. (1992) FEBS Lett. 300, 179-182; Lüers, G., Hashimoto, T., Fahimi, H. D., and Völkl, A. (1993) J. Cell Biol. 121, 1271-1280). We have observed that substantial amounts of peroxisomal proteins are found together with "microsomes" (100,000 x g pellet) after subcellular fractionation of rat liver homogenates. In this study we have investigated the origin of these peroxisomal proteins by modified gradient centrifugation procedures in Nycodenz and by analysis of enzyme activity distributions, Western blotting, and immunoelectron microscopy. It is concluded that much of this material is confined to novel populations of "peroxisomes." Immunocytochemistry on gradient fractions showed that some vesicles were enriched in acyl-CoA oxidase and peroxisomal multifunctional enzyme ("catalase-negative") whereas others were enriched in catalase and thiolase ("acyl-CoA oxidase-negative"). Double immunolabeling experiments verified the strong heterogeneity in the protein contents of these vesicles and also identified peroxisomes varying in size from about 0.5 microns ("normal peroxisomes") to extremely small vesicles of less than 100 nm in diameter. The possibility that these vesicles may be related to different subcompartments of a larger peroxisomal structure involved in protein import and biogenesis will be discussed.

Endotoxin induces structure-function alterations of rat liver peroxisomes: Kupffer cells released factors as possible modulators

“…Therefore, lighter peroxisomes may represent peroxisomes in the process of maturation, 50,53 or peroxisomal particles generated due to fragmentation of peroxisomal reticulum. 52 The additional peak of peroxisomes in LPS-treated liver represents peroxisomes undergoing autophagy by lysosomes.…”

“…50,51 The observation of lighter density peroxisomes (1.14 g/cm 3 ) was a characteristic of the LPS-treated liver gradients. Peroxisomes of different densities have been described in normal 52 and regenerating rat liver. 53 Furthermore, peroxisomes are induced by conditions such as hypolipidemic drugs treatment, 50 cold shock, 54 and ischemia and reperfusion.…”

Peroxisome Subpopulations of the Rat Liver: Isolation by Immune Free Flow Electrophoresis

“…The heterogeneity of peroxisomes (POs) is a wellknown phenomenon that is substantiated or at least supported by several lines of evidence: (a) the demonstration of distinct types of the organelle exhibiting differences in size, shape, and protein composition even in the same tissue (Angermüller and Fahimi 1988;Schrader et al 1994); (b) the isolation of subpopulations by density gradient centrifugation that diverge in their buoyant densities (Aikawa et al 1991;Klucis et al 1991;Lüers et al 1993;Wilcke et al 1995); and (c) the identification of so-called peroxisomal "ghosts" instead of intact POs in severe peroxisomal disorders such as the Zellweger syndrome (Santos et al 1988). Despite the accumulation of such data, a detailed characterization of appropriately divergent subsets of POs has yet to be performed.…”

Repair of Impaired Host Peroxisomal Properties Cropped Up Due to Visceral Leishmaniasis May Lead to Overcome Peroxisome Related Genetic Disorder Which May Develop Later After Treatment

“…When parasite burden was measured two months after administration of the last dose, no parasite was detected in hamster spleen or liver, and that gave indication towards the complete cure of the disease. The diameter of normal peroxisome is known to vary between 0.5 to 1.0 µm in animal tissues 171,172 . However, the average diameter of hamster liver peroxisome was found to be 0.37 µm.…”