The broad, long-term objective of this proposal is to understand the structure and function of the lamellar lipid assemblies that form the epidermal permeability barrier and govern the normal exfoliation and replacement of the epidermal surface cells. Several of the most common skin diseases, including psoriasis, ichthyoses, seborrheic dermatitis, dry skin, and acne, are thought to involve these epidermal lipid systems. Of particular interest, and presumed biological importance, is the recently discovered lipid sheath that is chemically attached to the outer ; I protein surface of each individual horny cell. It is proposed to determine the manner in which this lipid envelope is assembled, and to define the properties of the protein to which it becomes attached. Assembly of the precursor-molecules of the lipid envelope in their final location on the cell surface will be investigated by isolation and characterization of lamellar body bounding membranes that are directed to the epidermal cell surface during its final development. The protein to which the lipids become attached may be involucrin, which is known to contain the high proportion of glutamate residues necessary for linkage to the hydroxyceramides that constitute the corneocyte lipid envelope. The proportion of glutamate residues in the cross-linked protein envelope will be examined by solid state nuclear magnetic resonance techniques. The degree to which additional glutamate residues are provided by hydrolysis of glutamines will be studied by both chemical and NMR methods. Studies of the non-bound intercellular lipids, which constitute the water barrier in the stratum corneum, are aimed at determining how the unique lamellar patterns are produced and how they contribute to epidermal function. This will involve in vitro emulation of the succession of morphologic changes of lipid assemblies involved in epidermal cell differentiation, by manipulating the lipid composition of synthetic bilayer systems. Interactions within and between the intercellular lamellae and the corneocyte lipid envelopes will also be examined by biophysical and NMR techniques.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR032374-11
Application #
2078838
Study Section
General Medicine A Subcommittee 2 (GMA)
Project Start
1993-08-01
Project End
1997-07-31
Budget Start
1995-08-01
Budget End
1996-07-31
Support Year
11
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Iowa
Department
Dermatology
Type
Schools of Medicine
DUNS #
041294109
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Stewart, M E; Downing, D T (2001) The omega-hydroxyceramides of pig epidermis are attached to corneocytes solely through omega-hydroxyl groups. J Lipid Res 42:1105-10
Lazo, N D; Downing, D T (2001) Effects of Na2SO4 on hydrophobic and electrostatic interactions between amphipathic alpha-helices. J Pept Res 58:457-63
Stewart, M E; Downing, D T (1999) A new 6-hydroxy-4-sphingenine-containing ceramide in human skin. J Lipid Res 40:1434-9
Lazo, N D; Downing, D T (1999) A mixture of alpha-helical and 3(10)-helical conformations for involucrin in the human epidermal corneocyte envelope provides a scaffold for the attachment of both lipids and proteins. J Biol Chem 274:37340-4
Lazo, N D; Downing, D T (1999) Fibril formation by amyloid-beta proteins may involve beta-helical protofibrils. J Pept Res 53:633-40
Lazo, N D; Downing, D T (1998) Amyloid fibrils may be assembled from beta-helical protofibrils. Biochemistry 37:1731-5
Lazo, N D; Downing, D T (1998) Stabilization of amphipathic alpha-helical and beta-helical conformations in synthetic peptides in the presence and absence of ionic interactions. J Pept Res 51:85-9
Lazo, N D; Downing, D T (1997) Circular dichroism of model peptides emulating the amphipathic alpha-helical regions of intermediate filaments. Biochemistry 36:2559-65
Lazo, N D; Downing, D T (1997) Beta-helical fibrils from a model peptide. Biochem Biophys Res Commun 235:675-9
Downing, D T (1996) Chemical cross-linking between lysine groups in vimentin oligomers is dependent on local peptide conformations. Proteins 25:215-24

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