Date: 21 April 2023 (Fri)

Time: 5:00 p.m. - 6:00 p.m.

Venue: Cheung Kung Hai Lecture Theatre 1, G/F, William M.W. Mong Block, 21 Sassoon Road
 

5:00 p.m.

Presenter: Miss Yaoyue QI (PhD candidate)
Primary Supervisor: Dr. Cheng-han YU
Presentation Title: PI(3,4,5)P3-mediated Cdc42 activations control the macrophage podosome assembly
Abstract: Podosomes are actin-rich adhesion structures that contribute to macrophage migration through different tissues. Phosphatidylinositol and GTPase signalling are essential factors in regulating WASP-dependent F-actin polymerization of podosome. However, their signalling crosstalk and causality remain unclearly. We hypothesize that phosphatidylinositol biogenesis is the upstream signal to regulate GTPase activation. Indeed, we find that PI3K inhibition significantly reduces Cdc42-GTP levels, and WASP-3D mutant that is defective in Cdc42-GTP binding fails to participate in the podosome assembly. To identify PI(3,4,5)P3-dependent Cdc42 guanine exchange factors (GEFs), we apply quantitative imaging analysis and shRNA knockdown and find Vav family is promptly recruited to the plasma membrane in a PI(3,4,5)P3-dependent manner and is the critical factor in triggering the podosome assembly. Thus, PI3K activation is the upstream signal to recruit Cdc42-GEF Vav. Elevated levels of Cdc42-GTP then trigger WASP-mediated F-actin polymerization, podosome assembly, and macrophage migration.
 

5:30 p.m.

Presenter: Ms. Xiaoyu SUN (PhD candidate)
Primary Supervisor: Prof. Dong-yan JIN
Presentation Title: IFI16 is a novel cGAMP-binding protein that activates interferon production
Abstract: Cyclic dinucleotides such as cGAMP, c-di-GMP and c-di-AMP are second messengers in cell signaling. In bacteria, c-di-GMP plays critical roles in biofilm formation, virulence and quorum sensing. In mammals, 2’3’-cGAMP has evolved to trigger type I interferon production in the cGAS-STING signaling pathway in response to invasion of host cells by the incoming pathogens. However, unlike c-di-GMP, few cGAMP-binding proteins have been identified, and the function of its binding partners remain elusive. Here, we have found IFI16 to be a novel cGAMP-binding protein in fibroblast BJ5ta cells using cGAMP pull-down assay coupled to LC-MS analysis. The direct binding of IFI16 to cGAMP was validated by microscale thermophoresis (MST) and surface plasmon resonance (SPR) using purified proteins in vitro. Moreover, knockdown of IFI16 expression blunted the expression of IFN-β and ISGs stimulated by cGAMP. Thus, IFI16 is a novel cGAMP-binding protein critically involved in IFN production.

ALL ARE WELCOME

Should you have any enquiries, please feel free to contact Miss Cynthia Cheung at 3917 9748.