Angela M. Farrell

Propionibacterium acnes, a resident of lipid-rich human skin, produces a 33 kDa extracellular lipase encoded by gehA

Five independent clones of the Propionibacterium acnes P-37 lipase gene (gehA) were obtained in Escherichia coli, and the gene was localized to a 2.75 kb Xhol fragment by subcloning. The five clones were shown to contain the same gene by Southern blotting with a DIG-labelled probe to gehA. The nucleotide sequence of gehA was determined, and shown to contain a single ORF of 1017 kb, encoding a protein of 339 amino acids. The predicted molecular mass was 36 kDa. A 33 kDa (PAGE) radiolabelled polypeptide was detected from E. coli minicell preparations harbouring gehA, which could correspond to GehA after cleavage of the putative 26 amino acid residue signal peptide. gehA was overexpressed in E. coli under the control of the bacteriophage T7 promoter, and the corresponding polypeptide was found to be present in insoluble aggregates. Active lipase was produced when the overexpressing strain was incubated at a reduced temperature in the presence of sucrose. Purification of lipase from P. acnes culture supernatant fluids confirmed the production of a 33 kDa (PAGE) lipase.

Recessive x-linked ichthyosis: Role of cholesterol-sulfate accumulation in the barrier abnormality

Cholesterol sulfate is a multifunctional sterol metabolite, produced in large amounts in squamous keratinizing epithelia. Because patients with recessive x-linked ichthyosis display not only a 10-fold increase in cholesterol sulfate, but also a 50% reduction in cholesterol, we assessed here whether cholesterol sulfate accumulation and/or cholesterol deficiency produce abnormal barrier function in recessive x-linked ichthyosis. Patients with recessive x-linked ichthyosis display both an abnormal barrier under basal conditions, and a delay in barrier recovery after acute perturbation, which correlate with minor abnormalities in membrane structure and extensive lamellar-phase separation. Moreover, both the functional and the structural abnormalities were corrected by topical cholesterol. Yet, topical cholesterol sulfate produced both a barrier abnormality in intact skin and extracellular abnormalities in isolated stratum corneum, effects largely reversed by coapplications of cholesterol. Together, these results suggest that cholesterol sulfate accumulation rather than cholesterol deficiency is responsible for the barrier abnormality. Despite the apparent importance of cholesterol sulfate-to-cholesterol processing for normal barrier homeostasis, neither steroid sulfatase activity nor mRNA levels are upregulated following acute perturbations. These results demonstrate both a potential role for cholesterol sulfate-to-cholesterol processing in normal permeability barrier homeostasis, and that basal levels of steroid sulfatase are sufficient to accommodate acute insults to the permeability barrier.