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Technology
Receptor clustering is needed for many TNF SuperFamily receptors to transmit a full signal
The following TNFSF receptors are stimulated by many trimer forms of their respective ligands but not by 1-trimer forms: CD40; TNFR2; Fas; 4-1BB; DR3; DR5; TACI; and GITR.
Production of multi-trimer forms of soluble TNFSFs using multimerization scaffolds
MultimericBio's UltraTNFSFs are produced by genetically fusing the extracellular TNFSF domain with the body of a spontaneously multimerizing scaffold protein. Surfactant protein D (SP-D) is ideal because it is a self-assembling protein with four trimeric arms. For the SP-D versions of the UltraLigands, the protein is first synthesized within cells as a single polypeptide chain.
Left Panel: Each chain forms a trimeric “arm” within the cell. Middle Panel: Four arms come together at a “hub” to make a molecule with four TNFSF trimers that is then secreted. Right Panel: Further stacking at the hub can create higher order multimers of TNFSFs.
The UltraLigands are soluble, many trimer proteins that act like the membrane forms of TNFSFs.
One-trimer CD40L has little or no activity on resting cells in vitro. In contrast, UltraCD40L (i.e., 4-trimer SP-D-CD40L) is strongly activating. Similar results were shown for SP-D-CD40L by Haswell, Glennie, and Al-Shamkhani (Eur J Immunol. 31:3094-3100, 2001) and analogous data were presented for Acrp30-FasL by Holler et al in the group of Schneider and Tschopp (Mol Cellular Biol 23:1428-1440, 2003). Because the many trimer UltraTNFSFs cluster their receptors in responding cells, they have activities similar to the membrane forms of the TNFSFs, yet they can diffuse through tissues as soluble proteins.
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