Nucleoside transporters and activating kinases

Nucleoside transporters and activating kinases constitute the essential pathway for the pharmacological activity of nucleoside analog prodrugs (Source: PubMed PMID: 21115623). The transporters, including the SLC29 (ENT) and SLC28 (CNT) families, mediate the transmembrane flux of these agents, which are otherwise too hydrophilic to cross the lipid bilayer (Source: UniProt P11138, O00398). Following entry, activating kinases such as deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1) perform the first, rate-limiting phosphorylation step (Source: PubMed PMID: 15591231). This metabolic activation is required for the drugs to reach their active triphosphate forms, which exert cytotoxic effects by inhibiting DNA polymerase or being incorporated into DNA, leading to chain termination and apoptosis (Source: PubChem). Clinical studies have shown that the expression levels of transporters like hENT1 are significant predictors of survival in patients treated with gemcitabine, particularly in pancreatic cancer (Source: PubMed PMID: 23633441). Resistance to these therapies often arises from the loss of transporter expression or diminished kinase activity, making this axis a focal point for biomarker development and therapeutic monitoring.

Other names

Nucleoside salvage pathwayNucleoside analog activation axisENT/CNT and dCK/TK systemNucleoside metabolic activation machinery

Nucleoside analogs are transported into cells via Equilibrative (SLC29) or Concentrative (SLC28) Nucleoside Transporters and are subsequently phosphorylated by rate-limiting activating kinases (e.g., dCK, TK1, TK2) into their active nucleotide triphosphate forms, which inhibit DNA/RNA synthesis and induce apoptosis.