PLATELET-DERIVED GROWTH-FACTOR LABELED TO COLLOIDAL GOLD FOR USE AS A MITOGENIC RECEPTOR PROBE

  • 1 January 1984
    • journal article
    • research article
    • Vol. 34  (2) , 281-286
Abstract
Studies by others utilizing 125I-PDGF [platelet-derived growth factor] indicated that target cells express a high affinity surface receptor for PDGF. Purified platelet-derived growth factor (PDGF) was bound to gold colloid particles to explore the interaction of PDGF with mouse 3T3 cells. The gold-PDGF complex consists of .apprx. 26 PDGF molecules electrostatically absorbed to gold colloid (.apprx. 14.1 nm). The gold-PDGF complex induced mitogenic stimulation similar to unbound PDGF, although a 5-6 fold greater amount of complexed PDGF was required for the same effect. Incubation of the gold-PDGF complex with 3T3 cells for 4 h at 4.degree. C revealed that 98% of the membrane binding was randomly distributed on the cell surface with respect to coated pits, with each cell binding 7000-11,000 complexes. Addition of a 20-fold excess of unlabeled PDGF reduced surface binding of the gold-PDGF complex by 87% (1230 probes/cell). Warming to 37.degree. C followed by time-interval fixation permitted visualization of endocytosis of the complexes in coated vesicles (1-3 min), internalization (3-15 min) and lysosomal accumulation (15-60 min). Pretreatment of cultures with monensin (2 h, 10 .mu.M) abolished receptor binding, internalization and subsequent mitogenesis of the gold-PDGF complex. PDGF may require a surfce receptor to elicit mitogenesis.