Functional Characterization of Sodium-Dependent Multivitamin Transporter in MDCK-MDR1 Cells and Its Utilization as a Target for Drug Delivery

Abstract

The objective of this research is to characterize a sodium-dependent multivitamin transporter (SMVT) in MDCK-MDR1 cells (Madin-Darby canine kidney cells transfected with the human MDR1 gene) and to investigate the feasibility of utilizing MDCK-MDR1 cell line as an in vitro model to study the permeability of biotin-conjugated prodrugs of anti-HIV protease inhibitors. Mechanism of [ 3 H] biotin uptake and transport was delineated. Transepithelial permeability of the biotin conjugated prodrug i.e. biotin-saquinavir was also studied. Reverse transcription-polymerase chain reaction (RT-PCR) was carried out to confirm the existence of SMVT in MDCK-MDR1 cells. Biotin uptake was Na + , pH, and temperature dependent, but energyindependent. Transepithelial transport studies of biotin-saquinavir in MDCK-MDR1, wild type MDCK, and Caco-2 cells revealed that permeability of biotin-saquinavir was similar in all three cell lines. A band of SMVT mRNA at 862 bp was identified by RT-PCR. A sodium-dependent multivitamin transporter, SMVT, responsible for biotin uptake and transport, was identified and functionally characterized in MDCK-MDR1 cells. Therefore, MDCK-MDR1 cell line may be utilized as an in vitro model to study the permeability of biotin conjugated prodrugs such as HIV protease inhibitors.

A Minireview: Usefulness of Transporter-Targeted Prodrugs in Enhancing Membrane Permeability

“…124 Biotin-SQV decreased uptake and influx transport of [ 3 H]biotin in MDCK-MDR1 cells, indicating biotin-SQV is recognized by SMVT. The transepithelial transport of biotin-SQV in MDCK-MDR1, wild-type MDCK, and Caco-2 cells were comparable, indicating biotin-SQV can circumvent P-gp-and MRP2-mediated efflux transport.…”

Mechanisms of Biotin Transport

“…The optimum temperature for uptake was determined to be 30°C, and optimum pH ranged from 3.8 to 4.0 for total or free biotin and 2.8 to 7.0 for protein-bound biotin [76]. Uptake was also controlled by the biotin concentration in the growth medium [77,78]. VHT1 shows high selectivity for biotin and close structural analogues.…”

“…Using radiolabeled biotin, the M was measured to be 3.3 μM. Uptake of the labeled-biotin was inhibited by non-labeled biotin and analogues such as homobiotin, norbiotin, desthiobiotin, oxybiotin, biotin sulfon, and biotinyl-p-nitrophenyl ester (BNP), but not by the precursor 7,8-diaminopelargonic acid (DAPA) nor biocytin (N-biotinyl-L-lysine) [75,78]. Although VHT1 belongs to the allantoate permease family it cannot\ translocate allantoate or other structurally related analogues such as ureidosuccinate and pantothenate [74,75].…”

“…The improved efficacy of the treatment was due to enhanced SMVT mediated uptake. Similarly, biotinylation and PEGylation of the anti-HIV protease inhibitor saquinavir has improved the pharmacokinetics of this drug through by improved cellular permeability and inhibition of P-glycopeptide mediated efflux [86]. Given the enormous potential of biotin-mediated approaches for drug delivery, more research is required to better understand substrate specificity and mechanism of biotin transporters in various species.…”

Biotinylated Bilirubin Nanoparticles as a Tumor Microenvironment‐Responsive Drug Delivery System for Targeted Cancer Therapy

“…Despite numerous examples of biotin‐mediated drug delivery for cancer therapy, the mechanism of how biotin‐tagged therapeutics or nanoparticles can be taken up by cancer cells is still poorly understood. A piece of evidence found in the previous reports,13 however, suggests that after binding of the biotin‐tagged nanoparticles or therapeutics to the biotin transporter (i.e., sodium‐dependent multivitamin transporter), the resulting complex may undergo “endocytosis.” Our observations also suggest that the cellular uptake of Dox is mediated by specific interactions between the biotin transporter on cancer cells and the biotin ligand in bt‐BRNPs, underscoring the potential of this system as a specific cancer‐targeting drug‐delivery carrier.…”