Cell Biology

Of DALIS and DRiPs

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Science  12 Mar 2004:
Vol. 303, Issue 5664, pp. 1583
DOI: 10.1126/science.303.5664.1583b

Dendritic cells of the immune system respond to inflammatory signals by undergoing a process of maturation that equips them for antigen processing and presentation. In mature dendritic cells, polyubiquitinated proteins are sorted to intracellular aggregates that have been termed DALIs (for dentritic cell aggresome-like induced structures). DALIs only form when protein synthesis is ongoing; inhibition of protein synthesis leads to their disassembly. Lelouard et al. examined what processes are involved in targeting defective proteins and peptides to DALIs. In the presence of the peptide elongation inhibitor puromycin, incompletely synthesized proteins accumulate. These defective ribosomal products (or DRiPs) were observed to be stored rapidly in DALIs, where they were protected from degradation. Neither an intact microtubule network nor the actin microfilament network was required for this targeting. The DALIs were the sites at which DRiPs appeared to become ubiquitinated. DriPs also form in the absence of puromycin, and the production of these products from self and viral antigens is important in MHC class I restricted antigen presentation. It thus appears that dendritic cells are able to regulate the degradation of DRiPs by producing DALIs and this, in turn, is likely to be important in regulating antigen processing and presentation. — SMH

J. Cell Biol. 164, 667 (2004).

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