Lysine Acetylation Reshapes The Downstream Signaling Landscape of Vav1 in Lymphocytes

Abstract

Rodríguez 2 ABSTRACT Vav1 works both as a catalytic Rho GTPase activator and an adaptor molecule. These functions, which are critical for T cell development and antigenic responses, are tyrosine phosphorylation-dependent. However, it is not known whether other posttranslational modifications can modulate the signaling output of this protein.Here, we show that Vav1 becomes acetylated in a stimulation-and SH2 domaindependent manner. We also demonstrate that the acetylation of four residues located in the catalytic, lysine rich and SH2 domains preferentially buffers the Vav1 adaptor function that favors the stimulation of the nuclear factor of activated T cells. As a result, it modifies the signaling diversification properties normally exhibited by Vav1 in lymphocytes. This new regulatory layer is not shared by Vav family paralogs.

Cancer‐associated mutations in VAV1 trigger variegated signaling outputs and T‐cell lymphomagenesis

“…Those mutations target residues present in the CH (D26G), PH (K404R), NSH3 (G648C), SH2 (A673V, R678Q), and CSH3 (D797N, R822Q) regions. Similar uncoupling effects have been observed before with mutations targeting specific tyrosine phosphorylation and lysine acetylation sites of the protein (Barreira et al , 2014, 2018; Rodríguez‐Fdez et al , 2020). In those cases, this effect has been associated with the freezing of the molecule in intermediary conformational states that precede the fully phosphorylated and activated condition (Barreira et al , 2014, 2018; Rodríguez‐Fdez et al , 2020).…”

“…The latter possibility seems more plausible, given that mutations in the SH2 and CSH3 also promote a similar dissociation of the activation of the RAC1 and NFAT (Fig 1E). Signaling uncoupling effects have been previously observed with lab‐made mutations targeting specific tyrosine phosphorylation and lysine acetylation sites of the protein (Barreira et al , 2014, 2018; Rodríguez‐Fdez et al , 2020).…”

“…Consistent with this, we have found that Vav1 R678Q cannot become tyrosine phosphorylated when ectopically expressed in Jurkat cells (Fig 3C). It is unlikely that the negative regulatory role of the R 678 residue is due to the participation of the VAV1 SH2 domain in the interaction of an inhibitory phosphorylation site of the molecule, because other mutations that inactivate this domain (e.g., G691V) trigger a full LOF rather than a GOF effect in the molecule (Zugaza et al , 2002; Rodríguez‐Fdez et al , 2020). In line with this, the second activating SH2 mutation found in this study that maps outside the phosphotyrosine‐binding site does not impair the overall phosphorylation levels of the protein (Fig 3C, residue A673V).…”

“…Against this wellestablished paradigm, we have found two NSCLC-associated SH2 mutations (R673V and R678Q) that unexpectedly cause the stimulation of the RAC1-dependent pathways (Fig 1C). Also, against the long-held consensus regulatory model for the Vav family, one of those mutations targets a residue in the phosphotyrosine-binding site (R 678 ) that is critical for the interaction with both the upstream protein tyrosine kinases and downstream effectors ( interaction of an inhibitory phosphorylation site of the molecule, because other mutations that inactivate this domain (e.g., G691V) trigger a full LOF rather than a GOF effect in the molecule (Zugaza et al, 2002;Rodr ıguez-Fdez et al, 2020). In line with this, the second activating SH2 mutation found in this study that maps outside the phosphotyrosine-binding site does not impair the overall phosphorylation levels of the protein (Fig 3C , residue A673V).…”

“…À/À recipient mice(Menacho-Marquez et al, 2013;Lorenzo-Mart ın et al, 2020). This lymphopenic mouse strain was used to minimize the potential rejection of the transplanted cells due to neoantigen expression (Lorenzo-Mart ın et al, 2020).…”