Human platelets express heat shock protein receptors and regulate dendritic cell maturation.

Immunizations using the endoplasmic reticulum-resident heat shock protein Gp96 induce specific immune responses. Specificity is based on the major histocompatibility complex class I-restricted cross-presentation of Gp96-associated peptides derived from endogenous proteins. Initiation of the immune response depends on the ability of Gp96 to induce the production of proinflammatory cytokines by macrophages and dendritic cells (DCs) and of their maturation in a fashion presumably independent of associated peptide.

Importins fulfil a dual function as nuclear import receptors and cytoplasmic chaperones for exposed basic domains.

Many nuclear transport pathways are mediated by importin beta-related transport receptors. Here, we identify human importin (Imp) 4b as well as mouse Imp4a, Imp9a and Imp9b as novel family members. Imp4a mediates import of the ribosomal protein (rp) S3a, while Imp9a and Imp9b import rpS7, rpL18a and apparently numerous other substrates.