Scheme depicting how the recruitment of the exocyst at the IS is regulated. In resting conditions, Exo70 is mainly associated to the centrosome and inactive GEF-H1 to microtubules. BCR engagement enhances microtubule acetylation surrounding the centrosome, which releases Exo70 allowing its recruitment to the IS, and activates GEF-H1, which promotes the assembly of the exocyst complex to support local lysosome fusion at the synaptic membrane. Asterisk indicates that the localization of Sec3 and the site of exocyst assembly complex remain to be elucidated. APC, antigen-presenting cell.