Cyclin D3–cyclin-dependent kinase 6 complex (Cyclin D3–CDK6)

The Cyclin D3–CDK6 complex is a cell-cycle regulatory serine/threonine kinase composed of the protein cyclin D3 and cyclin-dependent kinase 6. It functions as a holoenzyme in the nucleus, controlling G1 phase progression and the G1/S transition by phosphorylating critical substrates, such as the retinoblastoma (RB) tumor suppressor protein. Beyond traditional cell cycle control, Cyclin D3–CDK6 directly regulates cancer cell metabolism by phosphorylating glycolytic enzymes (6-phosphofructokinase and pyruvate kinase M2), diverting glycolytic intermediates to the pentose phosphate and serine pathways, promoting survival and proliferation in tumors. High expression of the complex in tumors correlates with sensitivity to CDK4/6 inhibitors, making it a significant biomarker and therapeutic target. Targeted inhibition induces apoptosis by increasing reactive oxygen species. CDK4/6 inhibitors, such as palbociclib and ribociclib, are used clinically against various cancers. However, therapy is limited by hematologic toxicities and potential metabolic disruption[1][4][5].

Other names

Cyclin D3–CDK6 kinaseCDK6–cyclin D3 complexG1/S-specific cyclin-D3:CDK6 holoenzyme

Competitive inhibition of ATP binding site on CDK6. Preventing phosphorylation of cell-cycle substrates, notably Retinoblastoma protein (RB), and metabolic enzymes.