Broad cellular protein substrates

Broad cellular protein substrates is a collective term rather than a specific molecular entity, representing the diverse array of proteins within a cell that are simultaneously affected by a drug (Source: ChEMBL). This classification is typically applied to pharmacological agents with pleiotropic effects, such as non-specific alkylating agents or proteasome inhibitors, which do not discriminate between individual protein species (Source: NIH PubChem). In the context of targeted protein degradation, the term often refers to the "neo-substrates" recruited by molecular glues like thalidomide analogs to the E3 ubiquitin ligase complex (Source: Science, 2014). Because these substrates encompass a wide variety of functional classes—including transcription factors, enzymes, and structural proteins—their collective modulation leads to widespread cellular consequences such as apoptosis or cell cycle arrest (Source: Nature Reviews Drug Discovery, 2021). Consequently, this term is used to describe the scope of action for drugs that lack a single, discrete protein target. Due to this lack of specificity, therapeutic agents acting on broad substrates are often associated with significant systemic toxicity and narrow therapeutic windows (Source: Journal of Medicinal Chemistry).

Other names

Cellular proteinsTotal proteinProteome-wide substratesNeo-substrates

Non-specific covalent modification, cross-linking, or induced degradation of multiple cellular proteins.