ATP-sensitive association of mortalin with the IL-1 receptor type I.

Interleukin-1 (IL-1) is a major proinflammatory cytokine mediating local and systemic responses of the immune system. Two types of IL-1 receptors are known, but only the IL-1 receptor type I initiates biological responses. Here we show that two proteins with nucleic acid binding potential and mortalin, a member of the HSP70-family, are associated with the IL-1 receptor type I irrespective of IL-1 binding. The association of mortalin with the IL-1 receptor type I is specifically reversed by ATP concentrations in the physiological range. Other nucleotides are not or much less effective. The in vitro dissociation of mortalin effects neither the receptor association nor the activity of IRAK, which initiates the IL-1-dependent phosphorylation cascade. The roles of the receptor-associated proteins are therefore discussed in the context of receptor internalisation.