title: Syndecan-1, a cell-surface proteoglycan, changes in size and abundance when keratinocytes stratify.
abstract: In epidermis, keratinocytes in the basal cell layer differentiate, lose their attachment to the underlying extracellular matrix, and form extensive intercellular adhesions as they stratify. The alterations in cell-matrix and cell-cell adhesion required for keratinocyte stratification result from changes in the expression of numerous adhesion molecules. Syndecan-1, a member of a family of cell-surface proteoglycans, is known to bind cells to interstitial matrix. Syndecan-1 localizes to specific layers of mouse epidermal keratinocytes; its expression is modest in the basal layer, heavy in the suprabasal layers, but absent from the most superficial, terminally differentiated layers. This layer-specific difference suggests that syndecan-1 expression changes with keratinocyte differentiation. To assess this hypothesis, syndecan-1 expression was evaluated before and after calcium-induced stratification and differentiation. Cells growing as an unstratified monolayer express a higher molecular mass form of syndecan-1 than do stratified cells (modal relative mass of 160 kD versus 110 kD). This structural difference is due to larger and more heparan sulfate chains on syndecan-1 from monolayer cells. In addition, the amount of cell-surface syndecan-1 changes with stratification; stratified cultures show approximately 2.5 times more syndecan-1 per cell than do unstratified cultures, but do not significantly change the level of syndecan-1-specific mRNA. Thus, the structure and amount of syndecan-1 may be regulated to meet the changing adhesive requirements of stratifying keratinocytes.
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine, California.
authors.forename: R D
authors.initials: RD
authors.lastname: Sanderson
authors.forename: M T
authors.initials: MT
authors.lastname: Hinkes
authors.forename: M
authors.initials: M
authors.lastname: Bernfield
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis; D002448:Cell Adhesion; D002454:Cell Differentiation; D017077:Culture Media, Conditioned / Q000737:chemistry; D006025:Glycosaminoglycans / Q000032:analysis; D015603:Keratinocytes / Q000737:chemistry* / Q000166:cytology; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D017077:Culture Media, Conditioned; D006025:Glycosaminoglycans; D012333:RNA, Messenger; D002118:Calcium