PROXIMITY OSCILLATIONS OF COMPLEMENT TYPE-4 (ALPHA(X)BETA(2)) AND UROKINASE RECEPTORS ON MIGRATING NEUTROPHILS

Migrating neutrophils utilize beta(2) integrins for substrate attachme nt and urokinase receptors (uPAR) to focus pericellular proteolysis. O ur studies show that CR3 associates with uPAR on resting cells, wherea s uPAR associates with CR4 at lamellipodia of migrating cells. Using r esonance energy transfer (RET) microscopy, we show that the molecular proximity between CR4 and uPAR oscillates on migrating cells, thus sug gesting that CR4 molecules periodically bind/release uPAR. Cell contac t with fibrinogen, endothelial cells, chemotactic factors and indometh acin, and treatment with sub-optimal doses of signal transduction inhi bitors, affect the oscillations' period, amplitude, and/or waveform. T he oscillations were indistinguishable in period and 180 degrees out-o f-phase with cytosolic NAD(P)H autofluorescence oscillations. Thus, CR 4 and CR3 identify a neutrophil's axis of migration and CR4 may restra in uPAR at lamellipodia. Oscillations in signal transduction and energ y metabolism may coordinate cell adherence, local proteolysis, oxidant release, actin assembly, and cell extension.