Steroid sulfatase. Biosynthesis and processing in normal and mutant fibroblasts

Area of Science:

• Biochemistry
• Molecular Biology
• Dermatology

Background:

• Steroid sulfatase (STS) is an enzyme involved in steroid metabolism.
• X-linked ichthyosis (XLI) is a genetic disorder characterized by dry, scaly skin.
• Understanding STS biosynthesis is crucial for investigating XLI pathogenesis.

Purpose of the Study:

• To investigate the biosynthesis and processing of steroid sulfatase in human skin fibroblasts.
• To characterize the molecular forms and half-life of STS.
• To examine STS expression in fibroblasts from patients with X-linked ichthyosis.

Main Methods:

• Antibodies against purified human placental STS were used for detection.
• Biosynthesis was tracked in cultured human skin fibroblasts.
• Enzyme processing was analyzed using endoglucosaminidase H and 1-deoxy-manno-nojirimycin.
• STS-related polypeptides and activity were assessed in patient-derived fibroblasts.

Main Results:

• STS is initially synthesized as a membrane-bound Mr-63,500 polypeptide with N-linked oligosaccharides.
• Within 48 hours, STS is processed to a mature Mr-61,000 form via oligosaccharide modification.
• Oligosaccharide processing involves mannosidase(s) sensitive to 1-deoxy-manno-nojirimycin.
• The half-life of STS polypeptides was determined to be approximately 4 days.
• No detectable STS-related polypeptides or activity were found in fibroblasts from four XLI patients.

Conclusions:

• Human skin fibroblasts synthesize and process steroid sulfatase through distinct precursor and mature forms.
• The observed processing pathway involves specific enzymatic modifications of oligosaccharide chains.
• The absence of STS synthesis and activity in XLI fibroblasts confirms the role of STS deficiency in the disorder.