The Effect of Cis-4-Hydroxy-L-Proline on Intracellular Degradation of Newly Synthesized Collagen by Freshly Isolated Chick Tendon Fibroblasts

Abstract

Freshly isolated embryonic chick tendon cells were incubated for 6 hrs in suspension culture in the presence of the proline analogue, cis-4-hydroxyproline to cause the cells to synthesize collagen which was incapable of becoming triple helical. The cells were evaluated for the percentage of total protein synthesis devoted to collagen and for the percentage of newly synthesized collagen which was rapidly degraded. Collagen production in the presence of cis-4-hydroxyproline was reduced from 25% to 7% of total protein synthesis. Under normal conditions the cells degraded 8% of their newly synthesized collagen but when the cells were incubated in the presence of cis-4-hydroxyproline, 25% of their total collagen synthesized was degraded to dialyzable peptides. The enhanced degradation of nonhelical, analogue containing collagen was inhibited by inhibitors of lysosome function. These observations provide support for the concept that fibroblasts are able to recognize and degrade a portion of their newly synthesized collagen, and that defective collagen may be selectively degraded by an intracellular lysosomal process. Enhanced intracellular degradation can in part explain the decrease in collagen production by freshly isolated tendon fibroblasts incubated with cis-4-hydroxyproline.

Differentiation of axon-related Schwann cells in vitro: II. Control of myelin formation by basal lamina

“…A mechanism to account for the effect of ascorbic acid on SC collagen biosynthesis is well established in the literature: Ascorbic acid acts as a cofactor for prolyl hydroxylase which forms, from collagen-bound proline, the hydroxyproline residues essential for the formation and stabilization of the collagen triple-helix (reviewed by Prockop et al, 1976;Kivirikko and Myllyla, 1982). There is evidence suggesting that, at least for interstitial (fibrous) collagens, the lack of a triple-helical conformation increases the susceptibility of collagen chains to degradation intracellularly soon after synthesis (Berg et al, 1980;Neblock and Berg, 1982) and also reduces the rate of secretion of collagen chains, the net result being a severely reduced rate of appearance of functional collagen at the cell surface. Less is known about the role of the triple-helix in type IV collagen secretion and function.…”

Extracellular matrix synthesis is required for the movement of sclerotome and neural crest cells on collagen

“…As proline analogs, cis-HP and LACA are well established as agents that inhibit the secretion and deposition of triple helical procollagen from cells [4, 16, 271. However, although the primary biochemical targets of these drugs is in the collagen biosynthetic pathway, it must be emphasized that effects due to perturbation of interlinked processes cannot be entirely eliminated. Both cis-HP [18,20,21,29,42,501 and LACA [l, 8,9,18,20,29,38,421 have been used repeatedly for such inhibition, frequently with chick embryo tissue [5,17,40,49,511. The capacity of NPXP to inhibit proteoglycan synthesis is also well known [6,26,36,371.…”

Enhanced intrinsic biomechanical properties of osteoblastic mineralized tissue on roughened titanium surface

“…Prolyl 4‐hydroxylase (P4H) is a key enzyme during post‐translational modification of collagen chains,24–26 a process necessary to cross‐link individual molecules into a trimetric collagen molecule. Newly synthesized procollagens are degraded intracellularly at body temperature when they are not hydroxylased by P4H 27–29. P4H, to become active enzyme, forms α 2 β 2 tetramers in which the β subunit is identical to protein disulfide isomerase (PDI) 24, 25.…”