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- Title
Molecular Cloning and Expression of a Novel Keratinocyte Protein (Psoriasis-associated fatty acid-binding protein [PA-FABP]) that Is Highly Up-Regulated in Psoriatic Skin and that Shares Similarity to Fatty Acid-Binding Proteins.
- Authors
Madsen, Peder; Rasmussen, Hanne H.; Leffers, Henrik; Honoré, Bent; Celis, Julio E.
- Abstract
Analysis by means of two-dimensional (2D) gel electrophoresis of the protein patterns of normal and psoriatic unfractionated non-cultured keratinocytes has revealed a few low-molecular-weight proteins that are highly up-regulated in psoriatic skin. These include psoriasin; calgranulin B, also known as MRP 14, L1, or calprotectin; calgranulin A or MRP 8; and cystatin A or stefin A. Here, we have cloned and sequenced the cDNA (clone 1592) encoding a new member of this group of low - molecular-weight proteins [isoelectric focusing (IEE) SSP 3007 in the keratinocyte 2D gel protein database] that we have termed PA-FABP (psoriasis-associated fatty acid - binding protein). The deduced sequence predicted a protein with molecular weight of 15,164 daltons and a calculated pI of 6.96, values that are close to those recorded in the keratinocyte 2D gel protein database. The protein comigrated with PA-FABP as determined by 2D gel analysis of [35S]-methionine - labeled proteins expressed by transformed human amnion (ANA) cells transfected with clone 1592 using the vaccinia virus expression system and reacted with a rabbit polyclonal antibody raised against 2D gel purified PA-FABP. Structural analysis of the amino acid sequence revealed 48%, 52%, and 56% identity to known low-molecular-weight fatty acid - binding proteins belonging to the FABP family. Northern blot analysis showed that PA- FABP mRNA is indeed highly up-regulated in psoriatic keratinocytes. The transcript is present in human cell lines of epithelial and lymphoid (Molt 4) origin but cannot be detected in normal or SV40 transformed MRC-5 fibroblasts. 2D gel protein analysis of normal primary keratinocytes cultured for at least 8d under conditions that promoted incomplete terminal differentiation [serum-free keratinocyte (SFK) medium supplemented with epidermal growth factor (EGF), pituitary extract, and 10% fetal calf serum] revealed a strong up-regulation of PA-FABP, psoriasin, calgranulins A and B, and a few other proteins that are highly expressed in psoriatic skin. The levels of these proteins exceeded by far those observed in non-cultured normal keratinocytes implying that the cultured cells have followed an altered pattern of differentiation that resembles--at least in part--that of non-cultured psoriatic keratinocytes. The implications of these results for the study of psoriasis are discussed.
- Subjects
MOLECULAR cloning; KERATINOCYTES; CARRIER proteins; FATTY acids; PSORIASIS; FIBROBLASTS
- Publication
Journal of Investigative Dermatology, 1992, Vol 99, Issue 3, p299
- ISSN
0022-202X
- Publication type
Article
- DOI
10.1111/1523-1747.ep12616641