Targeting the Cerebrovascular Large Neutral Amino Acid Transporter (LAT1) Isoform Using a Novel Disulfide-Based Brain Drug Delivery System

Killian, Dennis M.; Hermeling, Suzanne; Chikhale, Prashant J.

doi:10.1080/10717540600559510

Cited by 43 publications

(33 citation statements)

References 25 publications

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“…45 However, when the drug is conjugated to the thiol group of cysteine, the small neutral amino acid is converted into a large neutral amino acid, and significant BBB transport via LAT1 was observed. 76 This case shows that a CMT substrate can be used as a drug carrier, providing the original structural characteristic of the substrate class for the targeted CMT system is retained.…”

Section: Drug Transport Into Brain Via Blood-brain Barrier Carrier-mementioning

confidence: 92%

“…A novel example is the case where a nontransportable drug is coupled to the thiol group of L-cysteine. 76 Cysteine is a small neutral amino acid, which has a low affinity for LAT1. 45 However, when the drug is conjugated to the thiol group of cysteine, the small neutral amino acid is converted into a large neutral amino acid, and significant BBB transport via LAT1 was observed.…”

Section: Drug Transport Into Brain Via Blood-brain Barrier Carrier-mementioning

confidence: 99%

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Drug Transport across the Blood–Brain Barrier

Pardridge¹

2012

J Cereb Blood Flow Metab

1,402

1,058

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The blood-brain barrier (BBB) prevents the brain uptake of most pharmaceuticals. This property arises from the epithelial-like tight junctions within the brain capillary endothelium. The BBB is anatomically and functionally distinct from the blood-cerebrospinal fluid barrier at the choroid plexus. Certain small molecule drugs may cross the BBB via lipid-mediated free diffusion, providing the drug has a molecular weight <400 Da and forms <8 hydrogen bonds. These chemical properties are lacking in the majority of small molecule drugs, and all large molecule drugs. Nevertheless, drugs can be reengineered for BBB transport, based on the knowledge of the endogenous transport systems within the BBB. Small molecule drugs can be synthesized that access carrier-mediated transport (CMT) systems within the BBB. Large molecule drugs can be reengineered with molecular Trojan horse delivery systems to access receptor-mediated transport (RMT) systems within the BBB. Peptide and antisense radiopharmaceuticals are made brain-penetrating with the combined use of RMT-based delivery systems and avidin-biotin technology. Knowledge on the endogenous CMT and RMT systems expressed at the BBB enable new solutions to the problem of BBB drug transport.

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Section: Drug Transport Into Brain Via Blood-brain Barrier Carrier-mementioning

confidence: 92%

Section: Drug Transport Into Brain Via Blood-brain Barrier Carrier-mementioning

confidence: 99%

Drug Transport across the Blood–Brain Barrier

Pardridge¹

2012

J Cereb Blood Flow Metab

1,402

1,058

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“…1) might interact with Cys384's free thiol (34) include (i) thiol nucleophilic attack on the thiocarbonyl as proposed for thiosemicarbazone inhibition of cysteine proteases (39), (ii) transition metal mediated interaction (40,41), and (iii) disulfide bond formation between the thiosemicarbazone's sulfur and Cys384's free thiol (42,43). These mechanisms could contribute to BLT-1's high potency.…”

Section: Resultsmentioning

confidence: 99%

Exoplasmic cysteine Cys384 of the HDL receptor SR-BI is critical for its sensitivity to a small-molecule inhibitor and normal lipid transport activity

Romer

Nieland

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The HDL receptor, scavenger receptor, class B, type I (SR-BI), is a homooligomeric cell surface glycoprotein that controls HDL structure and metabolism by mediating the cellular selective uptake of lipids, mainly cholesteryl esters, from HDL. The mechanism underlying SR-BI-mediated lipid transfer, which differs from classic receptor-mediated endocytosis, involves a two-step process (binding followed by lipid transport) that is poorly understood. Our previous structure/activity analysis of the small-molecule inhibitor blocker of lipid transport 1 (BLT-1), which potently (IC 50 ∼ 50 nM) blocks SR-BI-mediated lipid transport, established that the sulfur in BLT-1's thiosemicarbazone moiety was essential for activity. Here we show that BLT-1 is an irreversible inhibitor of SR-BI, raising the possibility that cysteine(s) in SR-BI interact with BLT-1. Mass spectrometric analysis of purified SR-BI showed two of its six exoplasmic cysteines have free thiol groups (Cys251 and Cys384). Converting Cys384 (but not Cys251) to serine resulted in complete BLT-1 insensitivity, establishing that the unique molecular target of BLT-1 inhibition of cellular SR-BI dependent lipid transport is SR-BI itself. The C384S substitution reduced the receptor's intrinsic lipid uptake activity by approximately 60% without dramatically altering its surface expression, homooligomerization, or HDL binding. Thus, a small-molecule screening approach identified a key residue in SR-BI involved in lipid transport, providing a powerful springboard into the analyses of the structure and mechanism of SR-BI, and highlighting the power of this approach for such analyses.

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“…LAT-1 is also an important drug target because it transports several prescription drugs, such as the antiparkinsonian drug L-dopa and the anticonvulsant gabapentin, across the BBB, thereby enabling their pharmacologic effects (3,4). This function at the BBB has made LAT-1 a target for drug delivery by modifying CNS-impermeable drugs such that they become LAT-1 substrates and have enhanced BBB penetration (5,6).…”

mentioning

confidence: 99%

Structure-based ligand discovery for the Large-neutral Amino Acid Transporter 1, LAT-1

Geier¹,

Schlessinger

Fan

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

158

207

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The Large-neutral Amino Acid Transporter 1 (LAT-1)-a sodiumindependent exchanger of amino acids, thyroid hormones, and prescription drugs-is highly expressed in the blood-brain barrier and various types of cancer. LAT-1 plays an important role in cancer development as well as in mediating drug and nutrient delivery across the blood-brain barrier, making it a key drug target. Here, we identify four LAT-1 ligands, including one chemically novel substrate, by comparative modeling, virtual screening, and experimental validation. These results may rationalize the enhanced brain permeability of two drugs, including the anticancer agent acivicin. Finally, two of our hits inhibited proliferation of a cancer cell line by distinct mechanisms, providing useful chemical tools to characterize the role of LAT-1 in cancer metabolism.arge-neutral Amino Acid Transporter 1 (LAT-1) is a sodiumindependent exchanger found in the brain, testis, and placenta, where it mediates transport of large-neutral amino acids (e.g., tyrosine) and thyroid hormones (e.g., triiodothyronine) across the cell membrane (1). More specifically, LAT-1 is highly expressed in the blood-and brain-facing membranes of the blood-brain barrier (BBB) to supply the central nervous system (CNS) with essential nutrients and to help maintain the neural microenvironment (2). LAT-1 is also an important drug target because it transports several prescription drugs, such as the antiparkinsonian drug L-dopa and the anticonvulsant gabapentin, across the BBB, thereby enabling their pharmacologic effects (3,4). This function at the BBB has made LAT-1 a target for drug delivery by modifying CNS-impermeable drugs such that they become LAT-1 substrates and have enhanced BBB penetration (5, 6).In addition, LAT-1 expression levels are increased in many types of cancer, including non-small-cell lung cancer and glioblastoma multiforme (GBM) (7,8). LAT-1 expression increases as cancers progress, leading to higher expression levels in highgrade tumors and metastases (9). In particular, LAT-1 plays a key role in cancer-associated reprogrammed metabolic networks by supplying growing tumor cells with essential amino acids that are used as nutrients to build biomass and signaling molecules to enhance proliferation by activating progrowth pathways such as the mammalian target of rapamycin (mTOR) pathway (10). Furthermore, inhibiting LAT-1 function reduces tumor cell proliferation, indicating that it may be a viable target for novel anticancer therapies (11-13). A cancer drug targeting LAT-1 can therefore be a LAT-1 inhibitor that deprives the cancer cells of nutrients or a cytotoxic LAT-1 substrate with an intracellular target (e.g., a metabolic enzyme).LAT-1 is a large protein with 12 putative membrane-spanning helices (14). To transport solutes across the membrane, LAT-1 binds SLC3A2, a glycoprotein with a single membrane-spanning helix that serves as a chaperone for LAT-1 (14). The atomic structure of human LAT-1 is not known, but LAT-1 exhibits significant sequence similarity to prokar...

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Targeting the Cerebrovascular Large Neutral Amino Acid Transporter (LAT1) Isoform Using a Novel Disulfide-Based Brain Drug Delivery System

Cited by 43 publications

References 25 publications

Drug Transport across the Blood–Brain Barrier

Drug Transport across the Blood–Brain Barrier

Exoplasmic cysteine Cys384 of the HDL receptor SR-BI is critical for its sensitivity to a small-molecule inhibitor and normal lipid transport activity

Structure-based ligand discovery for the Large-neutral Amino Acid Transporter 1, LAT-1

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