title: Modulation of triple-helical stability and subsequent melanoma cellular responses by single-site substitution of fluoroproline derivatives.
abstract: Collagen is a multifunctional protein, serving as a structural scaffold and a modulator of cellular responses. Prior work has identified distinct regions from several collagen types that promote cell adhesion, spreading, migration, and signal transduction. One of these regions, alpha1(IV)1263-1277 from type IV collagen, mediates these responses via melanoma cell CD44-chondrotin sulfate proteoglycan receptors. In the study presented here, we have used a triple-helical model of alpha1(IV)1263-1277 to evaluate (a) conformational stability and (b) cellular responses based on single-site incorporation of trans-4-fluoro-L-proline (trans-Flp) or cis-4-fluoro-L-proline (cis-Flp) for trans-4-hydroxy-L-proline (trans-Hyp). The structural effects of cis-Flp and trans-Flp substitution were studied by circular dichroism and NMR spectroscopies. The peptide containing a single trans-Flp instead of trans-Hyp was slightly more thermally stable than the parent peptide (T(m) = 37 vs 34 degrees C), while the peptide containing cis-Flp was considerably less stable than the parent peptide (T(m) = 30 degrees C). Melanoma cell adhesion and spreading were examined under conditions where the trans-Hyp-, trans-Flp-, and cis-Flp-containing ligands were approximately 15, <10, and approximately 65% denatured, respectively. Adhesion to each of the three ligands was remarkably sensitive to the respective ligand conformation, with EC(50) values of approximately 2.5, approximately 0.35, and >5.0 microM for the trans-Hyp-, trans-Flp-, and cis-Flp-containing ligands, respectively. Melanoma cell spreading was quantitated over a ligand concentration range of 0.01-50 microM and, in a fashion similar to adhesion, was more extensive on the trans-Flp ligand than on the trans-Hyp ligand. Very low levels of spreading were observed with the cis-Flp-containing ligand at all concentrations tested. Melanoma cell adhesion to and spreading on the three ligands suggested the dramatic biological consequence of even subtle changes in relative triple-helical content. Such subtle changes may model those occurring in the basement membrane during the tumor cell invasion process, and thus provide mechanistic insight into this stage of metastasis.
authors: Department of Chemistry and Biochemistry, Florida Atlantic University, 777 Glades Road, Boca Raton, Florida 33431-0991, USA.
authors: Navdeep B
authors: NB
authors: Malkar
authors: Janelle L
authors: JL
authors: Lauer-Fields
authors: Jeffrey A
authors: JA
authors: Borgia
authors: Gregg B
authors: GB
authors: Fields
mesh_terms: D000595:Amino Acid Sequence; D001485:Basement Membrane / Q000737:chemistry; D055592:Biophysical Phenomena; D001703:Biophysics; D002448:Cell Adhesion; D024141:Collagen Type IV / Q000737:chemistry* / Q000502:physiology; D004355:Drug Stability; D006801:Humans; D008024:Ligands; D008545:Melanoma / Q000737:chemistry* / Q000503:physiopathology*; D008969:Molecular Sequence Data; D009361:Neoplasm Invasiveness; D011392:Proline / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013237:Stereoisomerism; D014407:Tumor Cells, Cultured
chemical_list: D024141:Collagen Type IV; D008024:Ligands; C431803:fluoro-proline; D011392:Proline