FIGURE 5:

Cortexillin-null cells have delayed and diminished expression of cAR1 and ACA. Suspensions of WT and cortexillin-null cells in starvation buffer were pulsed with cAMP every 6 min for 8 h and aliquots taken every hour for protein analysis by Western blots: In WT cells, cAMP induced expression of both ACA (B) and cAR1 (C) with peaks at 6-7 h. ctxA⁻ and ctxB⁻ cells had delayed and reduced expression of ACA and cAR1, and ctxA⁻/B⁻ cells had almost no expression of either ACA or cAR1. The apparent doublets in the blots with anti-ACA are due to impurities in the polyclonal antibody. Actin expression was unaffected in the cortexillin-null cells (A). (D) Increase of cAMP-binding sites during cAMP pulsing of WT and cortexillin-null cells. Cell surface binding of [3H]cAMP to cell-surface receptors was determined as described under Materials and Methods. Cortexillin-null cells had a delayed and greatly reduced increase in cAMP-binding compared with WT cells. Data are representative of three independent experiments.