Antibodies for α4-integrin immunoprecipitation (PS/2 and HP2/1) and blotting (C-20) were from Millipore, GeneTex, and Santa Cruz Biotechnology, respectively. The phospho-α4-integrin antibody was generated as previously described (22 (link)). PKA subunit antibodies were supplied by Becton Dickinson. An anti–VCAM-1 antibody was from Southern Biotech. H89 was obtained from Millipore, and 8-bromoadenosine cAMP (8-Br-cAMP) was from Enzo Life Sciences. The PRKAR1β cDNA was obtained from GeneCopoeia. Streptozotocin (STZ) and anti-actin and control antibodies were from Sigma-Aldrich.