A non-receptor-mediated mechanism for internalization of molecular chaperones

Abstract

The evolving realization that stress proteins, which have for many years been considered to be exclusively intracellular molecules under normal conditions, can be released from viable cells via a number of potential routes/pathways has prompted interest into their extracellular biology and intercellular signaling properties. That the stress proteins Hsp60, Hsp70 and gp96 can elicit both pro- and anti-inflammatory effects suggests that these molecules play a key role in the maintenance of immunological homeostasis, and a better understanding of the immunobiology of extracellular stress proteins might reveal new and more effective approaches for controlling and managing infectious disease, inflammatory disease and cancer. A number of cell surface receptors for stress proteins have been identified, and the intracellular consequences of these cell surface receptor-ligand interactions have been characterized. To date, studies into the intercellular signaling properties of stress proteins and their interactions with antigen presenting cells have focused on specific receptor-mediated uptake, and have not considered the fact that such cells can also take up proteins via non-specific endocytosis/pinocytosis. Herein we present a methodological approach for assessing receptor-mediated and non-receptor-mediated uptake of gp96 by rat bone marrow-derived dendritic cells.

Fig. 1

Silver stained gels of electrophoresed unlabeled and FITC-labeled gp96 preparations (A), and unlabeled and FITC-labeled BSA preparations (B).

Fig. 2

Flow cytometric fluorescent histograms of rat BMDCs alone, and rat BMDCs following incubation with FITC-labeled BSA and FITC-labeled gp96 at 4°C (upper panel) and 37°C (lower panel). Histograms are representative of 2 independent experiments.