Aberrant Subcellular Localization of Peroxisomal 3-Ketoacyl-CoA Thiolase in the Zellweger Syndrome and Rhizomelic Chondrodysplasia Punctata

Abstract

ABSTRACT. Fibroblasts from patients with the inherited disorder Zellweger syndrome have few or no peroxisomes; multiple biochemical processes that normally occur in this organelle are defective. Rhizomelic chondrodysplasia punctata (RCDP) is another inherited disorder in which two unrelated peroxisomal metabolic processes, plasmalogen synthesis and phytanic acid oxidation, are impaired despite the normal appearance of peroxisomal structure. It was previously reported that one of the enzymes of peroxisomal fatty acid ,f3-oxidation, 3-ketoacyl-CoA thiolase (P-ketothiolase), was present in precursor rather than mature form in both of these diseases. Immunofluorescent staining for peroxisomal ,f3-ketothiolase showed the immunoreactivity to be localized in subcellular particles in fibroblasts from both Zellweger syndrome and RCDP patients, even though the former lack normal peroxisomes. Immunoblot studies were performed to determine the subcellular location of the thiolase precursor in fractionated fibroblasts from Zellweger and RCDP patients. In both disorders, thiolase immunoreactivity was detected in subcellular fractions having a lower density than normal peroxisomes and mitochondria, and was resistant to digestion by proteinase K.

The 22-kD Peroxisomal Integral Membrane Protein in Zellweger Syndrome—Presence, Abundance, and Association with a Peroxisomal Thiolase Precursor Protein

“…Our results, consistent with those of previous studies (40,43), suggest that the processing of the enzyme precursor is defective in Zellweger syndrome. Our results further suggest that in Zellweger syndrome peroxisomelike elements containing the 22-kD PMP and a 44-kD precursor protein of the P-oxidation enzyme thiolase are formed.…”

“…The 22-kD PMP associated membrane fraction and a peroxisomal thiolase precursor protein were consistently localized in the same low-density subcellular fractions, as already suspected by Balfe et al (40). These results argue against a general import failure of peroxisomal matrix proteins as the primary defect in Zellweger syndrome.…”

Pseudo Infantile Refsum's Disease: Catalase-Deficient Peroxisomal Particles with Partial Deficiency of Plasmalogen Synthesis and Oxidation of Fatty Acids

“…Although we did not perform immunocytochemistry to characterize these particles, we can assume that they are different from the peroxisomal particles described in other disorders of peroxisome biogenesis. They had higher density (1.137 g/cm3) than the membrane ghosts observed in Zellweger syndrome (I. I0 g/cm3) (1 6, 17), and RCDP (I. I -1.12 g/cm3) (13,15), and than w-particles (1.13 g/cm3) (18). Another difference is that membrane ghost structures and wparticles in Zellweger syndrome or RCDP do not contain enzyme activities for DHAP-AT and oxidation of VLCFA (15,18), whereas the peroxisome-like structures seen in our patient had significant activity for these enzymes.…”

“…RCDP differs from these disorders because peroxisomes are grossly normal in this disease and contain catalase. Moreover, only three peroxisomal functions are impaired (plasmalogen synthesis, oxidation of phytanic acid, and processing of @-ketothiolase) (1 [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Low-density particles (W-particles) containing catalase in Zellweger syndrome and normal fibroblasts.

“…More recently, we reported that a peroxisomal matrix enzyme, 3-ketoacyl-CoA thiolase (E.C. 2.3.1.16), could also be found associated with low-density membranous particles, at least in some Zellweger syndrome and rhizomelic chondrodysplasia punctata fibroblast lines, but in a larger molecular weight "unprocessed" form (7).…”