SIGNOR 4.0: the 2025 update with focus on phosphorylation data.

The SIGnaling Network Open Resource (SIGNOR 4.0, https://signor.uniroma2.it) is a database of manually curated causal interactions between biological entities. These signaling events are annotated along with their effect-denoting the activation or inactivation of a target entity-and mechanism through which it is mediated, such as phosphorylation, binding, or transcriptional regulation. The data is freely accessible and can be explored as customizable signaling networks, allowing users to adapt them for different modeling purposes. In our latest update (version 4.0), we improved our curation interface to include additional data-validation tools, integrated text-mining-assisted curation, increased our curation content, and expanded the scope of our curation efforts, with a particular emphasis on phosphorylation data. Furthermore, we developed a subdomain of SIGNOR, PhosphoSIGNOR, a dedicated user interface designed to enable targeted access to phosphorylation-specific information and network visualization. This expanded dataset allows for a more comprehensive mapping of signaling alterations and their associations with dysregulated cellular processes. The platform enables users to dynamically query phosphosite-specific data, examine context-dependent modifications, and integrate findings with known regulatory mechanisms. The PhosphoSIGNOR section of SIGNOR serves as an essential resource for cancer systems biology, offering an intuitive interface for hypothesis generation and mechanistic insights.