Adenomatous Polyposis Coli Modulates Actin and Microtubule Cytoskeleton at the Immunological Synapse to Tune CTL Functions

Abstract

Adenomatous polyposis coli (Apc) is a cell polarity regulator and a tumor suppressor associated with familial adenomatous polyposis and colorectal cancer. Apc involvement in T lymphocyte functions and antitumor immunity remains poorly understood. Investigating Apc-depleted human CD8 T cells and CD8 T cells from Apc Min/+ mutant mice, we found that Apc regulates actin and microtubule cytoskeleton remodeling at the immunological synapse, controlling synapse morphology and stability and lytic granule dynamics, including targeting and fusion at the synapse. Ultimately, Apc tunes cytotoxic T cell activity, leading to tumor cell killing. Furthermore, Apc modulates early TCR signaling and nuclear translocation of the NFAT transcription factor with mild consequences on the expression of some differentiation markers. In contrast, no differences in the production of effector cytokines were observed. These results, together with our previous findings on Apc function in regulatory T cells, indicate that Apc mutations may cause a dual damage, first unbalancing epithelial cell differentiation and growth driving epithelial neoplasms and, second, impairing T cell-mediated antitumor immunity at several levels. ImmunoHorizons, 2020, 4: 363-381.

Coordinating Cytoskeleton and Molecular Traffic in T Cell Migration, Activation, and Effector Functions

“…Hence, these data suggest that the association of NFAT with the microtubule network could facilitate concentration of this transcription factor around the nucleus and/or its interaction with nuclear pores. In agreement with a functional link between NFAT and the microtubules, we have also observed that knockdown of several proteins that control the appropriate organization of the microtubule network, such as the polarity regulators Apc and Dlg1 and the actincytoskeleton linker ezrin, impairs NFAT nuclear translocation and transcriptional activity Aguera-Gonzalez et al, 2017;Juzans et al, 2020). Altogether, these data underscore the involvement of microtubules in driving NFAT nuclear localization.…”

“…For instance, silencing of Dlg1 or Apc results in impaired F-actin remodeling, microtubule disorganization, and impaired centrosome and CD3 polarization at the synapse (Round et al, 2005;Humphries et al, 2012;Aguera-Gonzalez et al, 2017;Juzans et al, 2020). Therefore, Dlg1 and Apc modulate CTL immunological synapse formation and function, consequentially influencing both the lytic granule delivery to the synapse and the ability to kill target cells (Silva et al, 2015;Juzans et al, 2020). In addition, the impairment of actin regulators, such as WASP or the Arp2/3 complex, results in altered target cell elimination (De Meester et al, 2010;Randzavola et al, 2019).…”

“…Actin dynamics is thus necessary for efficient killing, while apparently not essential for lytic granule release. However, we have recently shown that Lamp1 cell surface measurement could not be sensitive enough to discriminate small secretion differences (Juzans et al, 2020).…”

“…Altering cytoskeleton organization and the interplay between cortical actin and microtubules affects synapse symmetry and stability (Ludford-Menting et al, 2005;Juzans et al, 2020). For instance, we have recently shown .…”

“…Alteration of the microtubule network is evident in Apc-silenced compared with control cells. Confocal images are from Juzans et al (2020). Bar = 5 µm.…”