The Journal of Immunology, Vol 142, Issue 3 842-847, Copyright © 1989 by American Association of Immunologists

ARTICLES

Biosynthesis of properdin

TC Farries and JP Atkinson
Howard Hughes Medical Institute Laboratories, St. Louis, MO 63110.

Properdin (P) is synthesized by the human promyelocytic cell line, HL- 60, after differentiation with DMSO. The secreted P was physiochemically indistinguishable from purified plasma P. It was polymerized and able to bind to C3IBb-Sepharose but not to C3i- Sepharose. No extracellular precursor was present. The intracellular form, detected between 1 and 4 h after labeling, was similar but had a slightly lower Mr. It also bound reversibly to C3iBb-Sepharose, and polymers could be demonstrated by cross-linking. Pulse-chase experiments suggested the existence of an earlier, but undetectable, intracellular precursor(s). This form could not be immunoprecipitated even when harsh solubilization conditions and/or antibodies against reduced and denatured P were utilized. Studies with endoglycosidases F and H and tunicamycin indicated that the detectable intracellular precursor contains high mannose N-linked carbohydrate that is processed to the complex form before secretion. The sugars are not required for polymerization, secretion, or functional activity, or responsible for the electrophoretic heterogeneity. Polymerization of P is therefore an early intracellular event, perhaps carefully controlled to prevent anomalous aggregation.

This article has been cited by other articles:

				S. Hartmann and J. Hofsteenge Properdin, the Positive Regulator of Complement, Is Highly C-Mannosylated J. Biol. Chem., September 8, 2000; 275(37): 28569 - 28574. [Abstract] [Full Text] [PDF]