Solute carrier organic anion transporter family member 1B1 (OATP1B1) (OATP1B1)

The hepatocyte uptake mechanism for microcystin and nodularin is primarily mediated by the Organic Anion Transporting Polypeptides (OATPs), specifically Solute carrier organic anion transporter family member 1B1 (OATP1B1) and 1B3 (OATP1B3) (Fischer et al., 2005, PMID: 15831567). These transporters are located on the sinusoidal (basolateral) membrane of hepatocytes and facilitate the sodium-independent uptake of various endogenous and exogenous compounds from the portal blood (Kalliokoski & Niemi, 2009, PMID: 19759158). Microcystins and nodularins, which are potent hepatotoxins produced by cyanobacteria, are large, hydrophilic molecules that cannot passively cross cell membranes; they exploit OATP1B1 and OATP1B3 to enter liver cells (Fischer et al., 2005, PMID: 15831567). Once inside, these toxins inhibit protein phosphatases 1 and 2A, causing cytoskeletal collapse and massive hepatic hemorrhage (MacKintosh et al., 1990, PMID: 2165532). Beyond toxin uptake, OATP1B1 is a critical determinant of the pharmacokinetics of many drugs, most notably statins, and is a major site for clinically significant drug-drug interactions (Niemi et al., 2011, PMID: 21115051). Genetic variations in the SLCO1B1 gene, such as the 521T>C polymorphism, can significantly reduce transporter function, leading to increased systemic drug exposure and an elevated risk of adverse effects like statin-induced myopathy (SEARCH Collaborative Group, 2008, PMID: 18755908). Therapeutic targeting of these transporters is often focused on avoiding inhibition to prevent drug-drug interactions or leveraging them for liver-specific drug delivery.

Other names

SLCO1B1OATP-COATP2LST-1Organic anion transporting polypeptide 1B1LST1

Facilitated diffusion and sodium-independent uptake of organic anions from the sinusoidal blood into hepatocytes.