A COMPARISON OF POSTRECEPTOR SIGNAL-TRANSDUCTION EVENTS IN JURKAT CELLS TRANSFECTED WITH EITHER IL-8R1 OR IL-8R2 - CHEMOKINE MEDIATED ACTIVATION OF P42/P44 MAP-KINASE (ERK-2)

The CXC chemokine, IL-8, is a potent chemoattractant of neutrophils and binds to two distinct receptors, termed IL-8R1 and IL-8R2. These receptors share high affinity for IL-8, however, only IL-8R1 is specific for IL-8 whereas IL-8R2 binds other related chemokines, including GRO alpha with high affinity, Stable Jurkat transfectants were generated expressing either functional IL-8R1 or IL-8R2 (J-IL8R1 and J-IL8R2), Both J-IL8R1 and J-IL8R2 exhibited high affinity IL-8 binding (K-d 3-5 nM) with respective receptor densities of 23,000 +/- 3,000 and 18,500 +/- 1,500, Pre-treatment of both transfectants with 1.0 mu g/ml B. pertussis toxin (PTx) resulted in inhibition of IL-8 mediated intracellular Ca2+ mobilisation and chemotaxis, without altering the receptor's affinity for its ligand. This indicates that both receptors couple to a PTx-sensitive G-protein. Further studies showed that IL-8R1 and IL-8R2 could mediate time-dependent phosphorylation of p42/p44 MAP-kinase. In both transfectants, phosphorylation was maximal at 1-2 min after IL-8 stimulation and could be inhibited by PTx, Stimulation of J-IL8R1 and J-IL8R2 with GRO alpha revealed that this chemokine was a more potent activator of MAP-kinase in J-IL8R2, an observation reflected in the high affinity binding of GRO alpha to IL-8R2, These studies indicate that chemokines are capable of activating protein kinases and with regards to PTx-sensitivity and MAP-kinase stimulation, no significant differences between IL-8R1 and IL-8R2 post-receptor signalling occur during cell activation by IL-8.