Authors:

Emma Litzelman

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About Paper:

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory loss and confusion. Late onset Alzheimer's Disease (LOAD), the most common type, typically begins after age 65 and lacks long-term treatment. However, recent studies identified Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) transporter as a potential therapeutic target. Src homology 2-containing-inositol-phosphatase 1 (SHIP1), overexpressed in LOAD and encoded by inositol polyphosphate-5-phosphatase (INPP5D), negatively regulates TREM2 mediated signaling by dephosphorylating membrane lipid PI(3,4,5)P3 to PI(3,4)P2, ultimately blocking PI3K/Akt activation and microglial phagocytosis. However, many aspects of SHIP1, including its oligomerization state identified in Dr. Mesecar's lab, remain unclear. The goal of this project is to understand the biological significance of SHIP1 oligomerization. The hypothesis is that one SHIP1 subunit's SH2 domain binds to the phosphorylated immunoreceptor tyrosine-based inhibitory motif (ITIM), anchoring it to help the other SHIP1 subunit interact with the immunoreceptor tyrosine-based activation motif ITAM on DAP12, the transmembrane region of TREM2. This anchor and assist mechanism stabilizes the protein near the membrane to dephosphorylate PIP3, which ultimately negatively regulating of TREM2 signaling pathway. To test this hypothesis, a SHIP1 construct with SH2 and dimerization domains was expressed and purified from E.coli. Its molecular weight and thermal stability were analyzed using mass photometry and nanoDSF. Binding affinity with phosphorylated and non-phosphorylated ITAM and ITIM motifs was assessed with microscale thermophoresis (MST). The construct is also being screened for crystallization for structural analysis by X-ray diffraction. This data will help in understanding molecular mechanisms controlling SHIP1 expression in AD. Keywords: LOAD; SHIP1; ITIM; ITAM; MST

Source:

Purdue University / 2024

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Co-authors:

Emma Litzelman