Investigating alternative signaling pathways regulated by Kindlin-3

• Main Author: Lee, Bernard Guan Hwee
• Other Authors: Tan Suet Mien
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Medicine, Health and Life Sciences; Leukemia
• Online Access: https://hdl.handle.net/10356/182569
• Institution: Nanyang Technological University

A three-membered, FERM-domain containing, focal adhesion protein family known as Kindlin mediates cellular adhesion and migration by promoting Integrin activation. This protein family comprises Kindlin-1, Kindlin-2 and Kindlin-3. Both Kindlin-1 and Kindlin-2 mediate the activation of various signaling pathways, whether Kindlin-3 plays a similar role remains to be studied. In this thesis, we examine the role Kindlin-3 plays in regulating alternative signaling pathways. Using PTEN-deficient T-ALL cells, we show that Kindlin-3 facilitates MAPK/ERK activation to promote cell proliferation by mediating DDR. Mechanistically, the Kindlin-3-RACK1-MEK1/2 ternary complex is transported to the PIP3- rich plasma membrane via Kindlin-3 binding to PIP3. Following PIP3 binding, RACK1- MEK1/2 dissociates from Kindlin-3, leading to RACK1 scaffolding MEK1/2 and b-RAF. This brings the MAPK/ERK components in proximity to promote MAPK/ERK activation. Ablation of Kindlin-3 expression leads to diminished ERK1/2 activation, elevated levels of DNA damage and delayed mitotic completion. Interestingly, the Kindlin-3 splice isoform, Kindlin-3L is unable to facilitate MAPK/ERK activation due to its poor PIP3-binding ability. During TCR activation, PIP3 production and Integrin LFA-1 activation promotes Kindlin-3 plasma membrane recruitment, contributing to MAPK/ERK activation. We also provide preliminary evidence that Kindlin-3 interacts with the cytokine receptor, IL2Rβ to facilitate its recruitment to the T-T homotypic synapse. Ablation of Kindlin-3 expression leads to diminished IL2Rβ levels at the T-T homotypic synapse. We identified the binding interface to be formed by the Kindlin-3 F0 subdomain and the C-terminal 21 amino acid stretch found within the IL2Rβ STAT binding region.