LEM-Domain-Containing Inner Nuclear Membrane Proteins: Emerging Regulators of Intranuclear Signaling

The LAP2–emerin–MAN1-domain (LEM-D) proteins constitute a family of inner nuclear membrane proteins that play essential roles in the spatial regulation of intranuclear signaling. Defined by the conserved LEM domain, these proteins interact with chromatin, nuclear lamins, and barrier-to-autointegration factor (BAF), thereby linking nuclear architecture to signal-dependent transcriptional control. This review summarizes current knowledge on the structural features and molecular functions of representative LEM-D proteins, including LAP2, emerin, and MAN1, with a particular focus on their emerging roles as regulators of intranuclear signaling pathways. We discuss how these proteins modulate the activity of transcription factors involved in Hedgehog, Wnt/β-catenin, STAT3, Notch, and transforming growth factor-β (TGF-β) signaling by temporally retaining them at the inner nuclear membrane and controlling their access to chromatin. Furthermore, this review highlights the physiological and pathological relevance of LEM-D-mediated signaling regulation, especially in the context of muscle development, regeneration, and nuclear envelope-associated diseases such as muscular dystrophies. By integrating structural, signaling, and disease-related perspectives, this review proposes a conceptual framework in which LEM-D proteins function as critical intranuclear signaling hubs. Understanding these mechanisms provides new insights into nuclear signal transduction and suggests potential therapeutic targets for diseases associated with nuclear envelope dysfunction.