Modulation of clearance of recombinant serum albumin by either glycosylation or truncation

Albumin is an abundant non-glycosylated plasma protein with a slow clearanc e profile. It has been employed as a fusion partner in efforts to slow the clearance of small antithrombotic proteins like hirudin, In the present stu dy, the in vivo clearance of recombinant rabbit serum albumin (rRSA), of mu tant rRSAs containing consensus sequences for N-linked glycosylation (D494N and V14T variants), and of mutant mini-proteins truncated at albumin domai n boundaries (rRSAs 1-185, 1-377, or 378-584) was examined. Mean terminal c atabolic half-lives (t(0.5)cat) in rabbits for plasma-derived RSA, rRSA, an d the V14T variant did not differ significantly (range 4.32-4.76 days). In contrast, mean t(0.5)cat was reduced to 2.87 days for the D494N variant and to less than 0.071 days for all mini-proteins. The mini-proteins were foun d in the urine in tissue distribution experiments, suggesting a renal route of clearance. Our results suggest that all three internally repeated album in domains are required to maintain the slow in vivo clearance profile of a lbumin, and that albumin glycosylation can be associated with an accelerati on of clearance. This information could be used to design fusion proteins, including those with antithrombotic properties, with predictably altered in vivo half-lives less than that of serum albumin. (C) 2000 Elsevier Science Ltd. All rights reserved.