Major peroxisomal membrane polypeptides are synthesized in cultured skin fibroblasts from patients with Zellweger syndrome.

Abstract

Biosynthesis of three major peroxisomal membrane polypeptides (70, 26, and 22 kD) were investigated in an attempt to account for the absence of peroxisomes in patients with Zellweger syndrome. Immunoblot analysis using membrane fractions of autopsied livers revealed that 70- and 22-kD polypeptides were deficient in three Japanese patients with this syndrome. However, pulse-labeling and chase experiments using cultured skin fibroblasts demonstrated that 70-, 26, and 22-kD polypeptides were synthesized in these patients at levels similar to those in the controls. No significant difference in the degradation rates of these polypeptides was noted between the patients and the controls. Subcellular fractionation after pulse-chase experiments revealed 70-kD polypeptides present in a membrane fraction of the cells. These observations indicate that at least 70-, 26-, and 22-kD peroxisomal membrane polypeptides are normally synthesized and considered to be transported into the disorganized peroxisomal membrane in patients with Zellweger syndrome. Molecular and functional analyses of these polypeptides are underway to clarify whether they contribute to membrane integrity or to the transport of peroxisomal matrix enzymes.