Fig. 1.
Pulse chase analysis of fibrillin-1 synthesis, secretion, and proteolytic processing indicates no intracellular processing of profibrillin-1. Neonatal fibroblasts were pulsed with [35S]cysteine for 15 min and then chased for various periods of time up to 6 h. The media and cell lysates (CL) were harvested and analyzed by 4% SDS–PAGE. A: Analysis of the cell lysate indicated that the higher migrating profibrillin-1 only was present in the CL. In the media, both profibrillin-1 and fibrillin-1 were present at 1 h. B: Immunoprecipitation of the CL using a fibrillin-1 polyclonal antibody directed against the proline-rich domain of the protein confirmed that only the profibrillin-1, the higher migrating form of the protein, was present in the CL. CL, cell lysate; M, media; profib-1, profibrillin-1; fib-1, fibrillin-1; RS, rabbit serum.