SLURP-1 Controls Growth and Migration of Lung Adenocarcinoma Cells, Forming a Complex With α7-nAChR and PDGFR/EGFR Heterodimer

Abstract

Secreted Ly6/uPAR-related protein 1 (SLURP-1) is a secreted Ly6/uPAR protein that negatively modulates the nicotinic acetylcholine receptor of α7 type (α7-nAChR), participating in control of cancer cell growth. Previously we showed, that a recombinant analogue of human SLURP-1 (rSLURP-1) diminishes the lung adenocarcinoma A549 cell proliferation and abolishes the nicotine-induced growth stimulation. Here, using multiplex immunoassay, we demonstrated a decrease in PTEN and mammalian target of rapamycin (mTOR) kinase phosphorylation in A549 cells upon the rSLURP-1 treatment pointing on down-regulation of the PI3K/AKT/mTOR signaling pathway. Decreased phosphorylation of the platelet-derived growth factor receptor type β (PDGFRβ) and arrest of the A549 cell cycle in the S and G2/M phases without apoptosis induction was also observed. Using a scratch migration assay, inhibition of A549 cell migration under the rSLURP-1 treatment was found. Affinity extraction demonstrated that rSLURP-1 in A549 cells forms a complex not only with α7-nAChR, but also with PDGFRα and epidermal growth factor receptor (EGFR), which are known to be involved in regulation of cancer cell growth and migration and are able to form a heterodimer. Knock-down of the genes encoding α7-nAChR, PDGFRα, and EGFR confirmed the involvement of these receptors in the anti-migration effect of SLURP-1. Thus, SLURP-1 can target the α7-nAChR complexes with PDGFRα and EGFR in the membrane of epithelial cells. Using chimeric proteins with grafted SLURP-1 loops we demonstrated that loop I is the principal active site responsible for the SLURP-1 interaction with α7-nAChR and its antiproliferative effect. Synthetic peptide mimicking the loop I cyclized by a disulfide bond inhibited ACh-evoked current at α7-nAChR, as well as A549 cell proliferation and migration. This synthetic peptide represents a promising prototype of new antitumor drug with the properties close to that of the native SLURP-1 protein.

New Three-Finger Protein from Starfish Asteria rubens Shares Structure and Pharmacology with Human Brain Neuromodulator Lynx2

“…Previously described values of IC 50 for human TFPs at different nAChRs expressed in oocytes lay in micromolar ranges. For example: IC 50 of Lypd6 at α3β4-nAChR is ~40 µM [ 15 ], IC 50 of Lynx1 at α7-nAChR is ~50 µM [ 46 ], and IC 50 of SLURP-1 at α7-nAChR is ~10 µM [ 47 ]. Thus, we used here the single concentration of Lystar5 (50 µM).…”

How is the AKT/mTOR pathway involved in cell migration and invasion?

“…Proteins that inhibit the upstream regulatory factor PTEN to activate AKT/mTOR The Phosphatase and tensin homolog (PTEN) gene was found to be a tumor suppressor closely related to tumorigenesis, and can encode the PTEN protein, which is composed of 403 amino acids. The PTEN protein, which has both lipid and protein phosphatase activity, has also been found to suppress tumorigenesis by directly dephosphorylating AKT in addition to inhibiting the activity of phosphorylated enzymes, such as receptor tyrosine kinases (Bu et al, 2021). As mentioned earlier, PIP3 binds with high affinity to the PH domain of AKT and can mediate its activation.…”

“…level, hindering the activation of AKT (Maehama and Dixon, 1998). It has also been documented that PTEN can directly interact with AKT to dephosphorylate AKT1 at the Ser473 and Thr308 sites, which in turn acts to suppress tumor development (Bu et al, 2021). Therefore, when the expression or activity of PTEN in cells is inhibited, its inhibitory effect on the AKT/mTOR pathway will also be attenuated, leading to the activation of AKT/mTOR and its downstream signals.…”

Membrane-mediated interaction of non-conventional snake three-finger toxins with nicotinic acetylcholine receptors

“…α7-nAChR is a homopentameric membrane protein consisting of an extracellular ligand-binding domain (α7-ECD), a transmembrane (TM) domain responsible for ionic conduction, and an intracellular domain with a large and flexible intracellular loop 9 . α7-nAChR has multiple functional states 10 and can interact with other receptors 11 , 12 , intracellular kinases 11 , and, probably, with G-proteins 13 . An important breakthrough in the structural studies of α7-nAChR interactions with the ligands was made using α7-ECD chimera with acetylcholine-binding protein (AChBP) from Lymnaea stagnalis 14 .…”