CXCL13 and posterior cortical atrophy: To further validate differences observed in Gα subunit(s) coupling and uncoupling to CXCR5 in CXCL13-treated versus untreated cells, we separately immunoprecipitated Gαq/11 and Gαi2 subunits in untreated and CXCL13-treated PCa cells and immunoblotted for CXCR5.