Cargo binding promotes KDEL receptor clustering at the mammalian cell surface

Abstract

Transmembrane receptor clustering is a ubiquitous phenomenon in pro- and eukaryotic cells to physically sense receptor/ligand interactions and subsequently translate an exogenous signal into a cellular response. Despite that receptor cluster formation has been described for a wide variety of receptors, ranging from chemotactic receptors in bacteria to growth factor and neurotransmitter receptors in mammalian cells, a mechanistic understanding of the underlying molecular processes is still puzzling. In an attempt to fill this gap we followed a combined experimental and theoretical approach by dissecting and modulating cargo binding, internalization and cellular response mediated by KDEL receptors (KDELRs) at the mammalian cell surface after interaction with a model cargo/ligand. Using a fluorescent variant of ricin toxin A chain as KDELR-ligand (eGFP-RTAH/KDEL), we demonstrate that cargo binding induces dose-dependent receptor cluster formation at and subsequent internalization from the membrane which is associated and counteracted by anterograde and microtubule-assisted receptor transport to preferred docking sites at the plasma membrane. By means of analytical arguments and extensive numerical simulations we show that cargo-synchronized receptor transport from and to the membrane is causative for KDELR/cargo cluster formation at the mammalian cell surface.

Exogenous supply of Hsp47 triggers fibrillar collagen deposition in skin cell cultures in vitro

“…2 c). These results demonstrate that Hsp47 uptake by cells is dependent on KDEL receptor display on the cell membrane, as suggested in earlier reports [46].…”

“…Hsp47 is retained in the ER via KDEL receptor mediated transport from the Golgi to the ER [26,30,[41][42][43][44][45]. This KDEL-receptor is also found on the cell membrane, [46] and is critical for the uptake of exogenous Hsp47 and transport to the ER of cells by simply adding the protein to the culture medium [23]. Expression levels of KDEL receptor at the cell membrane are cell-dependent [47,48].…”

A recombinant cholera toxin b subunit variant (CTB-KDEL) exhibits unique colon mucosal healing effects that have therapeutic implications for inflammatory bowel disease.

“…Consistent with these results, CTB-KDEL and CTB have shown comparable GM1binding affinity in ELISA, surface plasmon resonance, and flow cytometry analysis using the mouse macrophage cell line RAW264.7 [89]. Together, these results indicate that CTB-KDEL, but not CTB, facilitates TGFβ-mediated epithelial wound healing in the [108][109][110], it was hypothesized that CTB-KDEL could localize and remain in the ER for an extended period after retrograde transport [54]. To test this hypothesis, Caco2 cells were treated with CTB-KDEL or CTB then washed and incubated for 0, 12, 24 hours, followed by an immunoblot analysis to detect CTB and CTB-KDEL in the cell lysates.…”

Photoactivatable Hsp47: A Tool to Control and Regulate Collagen Secretion & Assembly

“…This motif is recognized by KDEL receptor after Hsp47 release in the Golgi and is responsible for its retention in the ER 41 KDEL sequence has been shown to block the retention of Hsp47 into the ER 42 . The KDEL receptor is also present in the plasma membrane of cells, and has been shown to assist internalization of KDEL containing molecules from the extracellular space [43][44][45] . We tested if our Hsp47 variants could be delivered to ER using KDEL receptormediated endocytosis (Fig.3).…”