Biology subjects

Gingras, A.

Publications and source records attributed to Gingras, A..

3 recordsLinked to original sources

bioRxiv2025

A CD25-CCR7 complex initiates non-canonical IL-2 signaling

IL-2, a central regulator of immune function, binds to its receptor subunit CD25 (IL-2R), promoting IL-2 interaction with {beta} and {gamma} subunits to trigger the canonical IL-2 signaling pathway. An anti-mouse CD25 antibody, PC61, triggers alternative IL-2 signaling, leading to integrin activation. PC61 induces a complex formed by the IL-2-dependent association of CD25 with CCR7, suggesting that the formation of this complex initiates alternative IL-2 signaling. Here, we used structure-based design together with combinatorial screening to identify an IL-2 mutant (denoted IL-2(E52K)) that spares canonical IL-2 signaling but disrupts both PC61-induced complex formation and integrin activation while retaining the full CD25 affinity of the parent molecule. We also report that heparan sulfate (HS), a physiological ligand of IL-2 that triggers alternative signaling, induced IL-2-dependent CD25-CCR7 association, whereas IL-2(E52K) failed to support both HS-induced CD25-CCR7 complex formation and integrin activation. Thus, both anti-CD25 antibody and HS require common features of IL-2 needed for CD25-CCR7 complex assembly and resulting integrin activation. Collectively, these data show that IL-2 promotes CD25 interaction with CCR7, thereby forming the signal initiating complex. Furthermore, canonical and alternative IL-2 signaling can be decoupled by an IL-2 mutation, creating a tool to specify the biological role of alternative IL-2 signaling in immune responses.

cell biology↗

bioRxiv2021

Phostensin Enables Lymphocyte Integrin Activation and Population of Peripheral Lymphoid Organs

Rap1 GTPase drives assembly of the Mig-10/RIAM/lamellipodin-Integrin-Talin (MIT) complex that enables integrin-dependent lymphocyte functions. Here we used tandem affinity tag-based proteomics to isolate and analyze the MIT complex and reveal that Phostensin (PTSN), a regulatory subunit of protein phosphatase 1, is a component of the complex. PTSN mediates de-phosphorylation of Rap1 thereby preserving the activity and membrane localization of Rap1 to stabilize the MIT complex. CRISPR/Cas9-induced deletion of PPP1R18, which encodes PTSN, markedly suppresses integrin activation in Jurkat human T cells. We generated apparently healthy Ppp1r18-/- mice that manifest lymphocytosis and reduced population of peripheral lymphoid tissues ascribable to defective activation of integrins L{beta}2 and 4{beta}7. Ppp1r18-/- T cells exhibit reduced capacity to induce colitis in a murine adoptive transfer model. Thus, PTSN enables lymphocyte integrin-mediated functions by dephosphorylating Rap1 to stabilize the MIT complex. As a consequence, loss of PTSN ameliorates T cell-mediated colitis. SUMMARYPhostensin, a protein phosphatase 1 regulatory subunit, supports lymphocyte integrin-dependent functions by mediating dephosphorylation of Rap1 to stabilize the MIT complex thereby enabling the population of peripheral lymphoid organs and T cell-mediated colitis.

immunology↗

bioRxiv2018

A Rap1 binding site and lipid-dependent helix in talin F1 domain cooperate in integrin activation

Rap1 GTPases bind effectors, such as RIAM, to enable talin1 to induce integrin activation. In addition, Rap1 binds directly to the talin1 F0 domain (F0); however, this interaction makes a negligible contribution to integrin activation in CHO cells or platelets. Here, we show that talin1 F1 domain contains a previously undetected Rap1 binding site of similar affinity to that in F0. A structure-guided point mutant (R118E) in F1, which blocks Rap1 binding, abolishes the capacity of Rap1 to potentiate talin1-induced integrin activation. The capacity of F1 to mediate Rap1-dependent integrin activation depends on a unique loop in F1 that transforms into an amphipathic helix upon binding to membrane lipids. Basic membrane-facing residues of this helix are critical as charge reversal mutations led to dramatic suppression of talin1-dependent activation. Thus, a novel Rap1 binding site and a lipid-dependent amphipathic helix in talin1 F1 cooperate to enable a direct Rap1-talin1 interaction to cause integrin activation.\n\nSummaryThis work reveals that Rap1 GTPases bind directly to talin1 F1 domain and by cooperating with a unique lipid-dependent amphipathic helix in the F1 domain effects talin1-mediated integrin activation.

cell biology↗