Novel reagents for labeling proteins in live and fixed cells
FAP reporters consist of a polypeptide unit (the FAP) and an organic small molecule unit (the fluorogen). Neither the FAP nor the fluorogen is fluorescent by itself, but together they form a complex that exhibits strong fluorescence due to conformational constraint of the fluorogen when bound by the FAP. Because the same FAP can be used with a variety of fluorogens of different spectral properties, the system allows one to do very informative experiments (e.g., pulse-chase experiments or differential labeling of the same protein in different cellular compartments) that are not possible using standard fluorescent proteins or chemical fluorophores. Gallo, Vasilev and Jarvik introduce new FAP-based immunodetection reagents that dramatically expand the range of the FAP-fluorogen system, making it possible to FAP tag almost any cellular protein to which a standard antibody is available.
Gallo et al., Biotechnol Bioeng 2014; 111:475–484.
Nodal modulates macrophage polarization
Nodal expression by tumor cells has long been known to increase tumorigenesis by inducing angiogenesis, and promoting metastasis. The role that Nodal plays in the polarization of tumor associated macrophages (TAMs), however, is less known. Wang et al. show that Nodal blockade in tumor microenvironment upregulates the production of IL-12 in macrophages and reverses TAMs back to an M1 phenotype. In contrast, exposure of murine macrophages to recombinant Nodal (rNodal) decreases the expression of IL-12 and polarizes cells towards an M2-like/TAM phenotype. Furthermore, rNodal-treated macrophages inhibit the proliferation of T lymphocytes and rNodal increases the phagocytic ability of macrophages. The data suggest that in the tumor microenvironment, Nodal has the capacity to influence the polarization of macrophages and the expression of IL-12, such that its blockade represents a potential target to promote anti-tumor immunity.
Wang et al., Eur J Immunol 2014; 44:173–183.