The ATP-binding cassette subfamily B member 1 (ABCB1), also known as P-glycoprotein (P-gp) or multidrug resistance protein 1 (MDR1), is a critical efflux transporter that plays a fundamental role in protecting the brain from xenobiotics and maintaining drug pharmacokinetics[1]. Encoded by the ABCB1 gene, this 170 kDa transmembrane protein utilizes ATP hydrolysis to actively extrude a wide range of substrates across cellular membranes[2].
ABCB1 is composed of two transmembrane domains (TMDs), each containing six transmembrane helices, and two nucleotide-binding domains (NBDs) that hydrolyze ATP to drive substrate translocation[3]. The protein adopts an inward-facing conformation in the absence of substrate and undergoes dramatic conformational changes to an outward-facing state during the transport cycle[4]. Key structural features include:
ABCB1 is highly expressed on the apical (luminal) surface of brain microvascular endothelial cells forming the blood-brain barrier (BBB)[5]. Here, it functions as a gatekeeper, preventing the accumulation of potentially neurotoxic compounds in the central nervous system:
Beyond the BBB, ABCB1 is expressed in various tissues:
ABCB1 plays complex roles in Alzheimer's disease pathogenesis:
| Drug Class | ABCB1 Interaction | Neurological Relevance |
|---|---|---|
| Antiepileptics | Substrate | Drug-resistant epilepsy |
| Antidepressants | Substrate | CNS penetration |
| Opioids | Substrate | Analgesia efficacy |
| Statins | Substrate | Brain availability |
| Tyrosine kinase inhibitors | Variable | Brain tumor therapy |
Several ABCB1 inhibitors have been investigated to overcome multidrug resistance:
Overcoming ABCB1-mediated efflux is a major focus for CNS drug development:
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