MAPK3 and AIDS: Beside heparin, also HSPGs of lymphoblastoid cell surface bind p17 favoring its oligomerization and are required to induce p17-dependent ERK1/2 phosphorylation, suggesting the possibility that, in vivo, p17 binding to HSPG and the following oligomerization at the cell surface are required for a full lymphoid cell activation, concurring to pathological effects exerted by p17 during AIDS progression.