Biology subjects

Klein, D. E.

Publications and source records attributed to Klein, D. E..

3 recordsLinked to original sources

bioRxiv2026

Structural Basis for MCAM Mediated Inhibition of Laminin Dependent Cell Migration

MCAM/CD146 is an immunoglobulin-superfamily receptor expressed on endothelial cells, immune cells and numerous carcinomas. Although MCAM has long been associated with metastatic progression, recent work has revealed context-dependent inhibitory effects on transendothelial migration, leaving unresolved how MCAM engagement of basement membrane laminins alters cell migration. Here, we report multiple cryo-electron microscopy structures of human MCAM bound to laminin. We show MCAM engages laminin on a surface centered on the first two laminin globular domains (LG1-2) and that this epitope directly overlaps with the interface used by integrin. Consistent with structural competition, MCAM occupation of laminin abolishes integrin-dependent cell migration. Structure-guided mutation of the MCAM-laminin interface disrupts laminin binding and eliminates MCAM-mediated inhibition. These findings establish that MCAM and integrin compete for a shared interface on laminin and define a structural mechanism by which MCAM occupancy can suppress laminin-dependent migration. The structure resolves a central ambiguity in MCAM biology and provides a framework for developing biologics that selectively modulate pathological cell migration.

biophysics↗

bioRxiv2024

Physical basis for the interaction between Drosophila ROS1 and the GPCR BOSS

Abstract/SummaryDrosophila ROS1 (dROS1, Sevenless) is a receptor tyrosine kinase (RTK) essential for the differentiation of Drosophila R7 photoreceptor cells1, 2. Activation of dROS1 is mediated by binding to the extracellular region (ECR) of the GPCR (G protein coupled receptor) BOSS (Bride Of Sevenless) on adjacent cells1, 3, 4. Genetic evidence together with in vitro activity assays confirmed the activation of dROS1 by BOSS and identified subsequent downstream signaling pathways including SOS (Son of Sevenless)1, 5. However, the physical basis for how dROS1 interacts with the GPCR BOSS has long remained unknown. Here we provide the first structure, using Cryo-Electron Microscopy (CryoEM), of dROS1s extracellular region, which mediates ligand binding. We show that the N-terminal region of dROS1 adopts a folded-over conformation harboring a novel structural domain. We further narrowed down the interacting binding epitopes on both dROS1 and BOSS. This includes a beta-strand in dROS1s third Fibronectin type III (FNIII) domain and the C-terminal portion of BOSS ECR. Our mutagenesis studies, coupled with AlphaFold complex predictions, support a binding interaction mediated by a hydrophobic interaction and beta-strand augmentation between these regions. Our findings provide a fundamental understanding of the regulatory function of dROS1 and further provide mechanistic insight into the human ortholog and oncogene ROS1.

biophysics↗

bioRxiv2022

7SK methylation Promotes Transcriptional Activity upon Growth Factor Stimulation

A fundamental facet of cell signaling is the conversion of extracellular signals into adaptive transcriptional responses. The role of RNA modifications in this process is poorly understood. The small nuclear RNA 7SK prevents transcription elongation by sequestering the complex CDK9/CCNT1 (P-TEFb). We discovered that METTL3 methylates 7SK. The m6A methylation of 7SK in turn promotes its binding to heterogeneous nuclear ribonucleoproteins (HNRNPs), with consequent release of the HEXIM1/P-TEFb complex - leading to the induction of growth factor-stimulated transcriptional responses. The methylation of 7SK relies on the activation of METTL3 via phosphorylation downstream of growth factors-signaling pathways such as the epidermal growth factor (EGF). Our findings establish a novel function for the m6A modification in converting growth-factor signaling events to a transcriptional elongation regulatory response via an RNA-methylation-dependent switch. One-Sentence Summarym6A methylation of the non-coding RNA 7SK promotes transcriptional activity upon growth factor stimulation.

molecular biology↗