* The sirtuins promote Dishevelled-1 scaffolding of TIAM1, Rac activation and cell migration.
- Rac1-GTPases serve as intermediary cellular switches, which conduct transient and constitutive signals from upstream cues, including those from Ras oncoproteins. Although the sirtuin1 (SIRT1) deacetylase is overexpressed in several human cancers and has recently been linked to cancer cell motility as a context-dependent regulator of multiple pathways, its role in Rac1 activation has not been reported. Similarly, SIRT2 has been demonstrated to be upregulated in some cancers; however, studies have also reported its role in tumor suppression. Here, we demonstrate that SIRT1 and SIRT2 positively regulate the levels of Rac1-GTP and the activity of T-cell lymphoma invasion and metastasis 1 (TIAM1), a Rac guanine nucleotide exchange factor (GEF). Transient inhibition of SIRT1 and SIRT2 resulted in increased acetylation of TIAM1, whereas chronic SIRT2 knockdown resulted in enhanced acetylation of TIAM1. SIRT1 regulates Dishevelled (DVL) protein levels in cancer cells, and DVL along with TIAM1 are known to augment Rac activation; however, SIRT1 or 2 has not been previously linked with TIAM1. We found that diminished sirtuin activity led to the disruption of the DVL1-TIAM1 interaction. We hence propose a model for Rac activation where SIRT1/2 positively modulates the DVL/TIAM1/Rac axis and promotes sustained pathway activation.
Overview of verb demonstrate
The verb demonstrate has 4 senses (first 4 from tagged texts)
1. (24) show, demo, exhibit, present, demonstrate -- (give an exhibition of to an interested
audience; "She shows her dogs frequently"; "We will demo the new software in Washington")
2. (22) prove, demonstrate, establish, show, shew -- (establish the validity of something, as by an
example, explanation or experiment; "The experiment demonstrated the instability of the compound";
"The mathematician showed the validity of the conjecture")
3. (2) attest, certify, manifest, demonstrate, evidence -- (provide evidence for; stand as proof of;
show by one's behavior, attitude, or external attributes; "His high fever attested to his illness";
"The buildings in Rome manifest a high level of architectural sophistication"; "This decision
demonstrates his sense of fairness")
4. (1) demonstrate, march -- (march in protest; take part in a demonstration; "Thousands
demonstrated against globalization during the meeting of the most powerful economic nations in
Seattle")
Overview of adj demonstrated
The adj demonstrated has 1 sense (first 1 from tagged texts)
1. (1) demonstrated -- (having been demonstrated or verified beyond doubt)
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