Peter Agre

Dr. Peter Agre, 2003 Nobel Prize winner in chemistry, is currently the director of the Johns Hopkins Malaria Research Institute. In addition to the Nobel Prize, Dr. Agre's honors include election to the National Academy of Sciences in 2000, the Institute of Medicine in 2005, the American Academy of Arts and Sciences in 2003, and the American Philosophical Society in 2004.

Dr. Agre's research in red-blood-cell biochemistry led to the first known membrane defects in congenital hemolytic anemias (spherocytosis) and produced the first isolation of the Rh blood group antigens. In 1992, his laboratory became widely recognized for discovering the aquaporins, a family of water channel proteins found throughout nature and responsible for numerous physiological processes in humans— including kidney concentration, as well as secretion of spinal fluid, aqueous humor, tears, sweat, and release of glycerol from fat.


Recent Submissions

Now showing 1 - 20 of 116
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    Man is not a rodent: aquaporins in the airways
    (American Thoracic Society, 2001-03) Agre, P; King, L S
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    Respiratory aquaporins in lung inflammation: the night is young
    (American Thoracic Society, 2000-01) Agre, P; Nielsen, S; King, L S
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    Linkage of dominant hereditary spherocytosis to the gene for the erythrocyte membrane-skeleton protein ankyrin
    (Massachusetts Medical Society, 1990-10-11) Forget, Bernard G.; Lux, Samuel E.; John, Katherine M.; Tang, Tang K.; Winkelmann, John C.; Watkins, Paul C.; Agre, Peter; Costa, Fernando F.
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    Aquaporin water channels [Nobel Lecture]
    (Gesellschaft Deutscher Chemiker, 2004) Agre, Peter
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    Defective cellular trafficking of lacrimal gland aquaporin-5 in Sjögren's syndrome
    (Elsevier, 2001-06-23) Ishida, Naruhiro; Agre, Peter; King, Landon S.; Hirai, Shinichiro; Tsubota, Kazuo
    Dry eyes and dry mouth are clinical hallmarks of Sjögren's syndrome. We assessed the distribution of aquaporin-5 (AQP5) in lacrimal gland biopsy samples. Healthy controls and patients with Mikulicz's disease or non-Sjögren's syndrome dry eye had the expected apical distribution of AQP5 in lacrimal acinar cells. By contrast, cytoplasmic AQP5 was seen in patients with Sjögren's syndrome. Sodium channel and sodium-potassium ATPase distributions were normal in all groups. These findings show a selective defect in lacrimal gland AQP5 trafficking in Sjögren's syndrome that might contribute to decreased lacrimation and dry eye in these patients.
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    Aquaporins in complex tissues. I. Developmental patterns in respiratory and glandular tissues of rat
    (American Physological Society, 1997-11) Agre, Peter; Nielsen, Søren; King, Landon S.
    Developmental expression of aquaporin water transport proteins is not well understood in respiratory tract or secretory glands; here we define aquaporin protein ontogeny in rat. Expression of aquaporin-3 (AQP3), AQP4, and AQP5 proteins occurs within 2 wk after birth, whereas AQP1 first appears before birth. In most tissues, aquaporin protein expression increases progressively, although transient high-level expression is noted in distal lung (AQP4 at postnatal day +2) and trachea (AQP5 at postnatal day +21 and AQP3 at postnatal day +42). In mature animals, AQP5 is abundant in distal lung and salivary glands, AQP3 and AQP4 are present in trachea, and AQP1 is present in all of these tissues except salivary glands. Surprisingly, all four aquaporin proteins are highly abundant in nasopharynx. Unlike AQP1, corticosteroids did not induce expression of AQP3, AQP4, or AQP5 in lung. Our results seemingly implicate aquaporins in proximal airway humidification, glandular secretion, and perinatal clearance of fluid from distal airways. However, the studies underscore a need for detailed immunohistochemical characterizations and definitive functional studies.
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    The three-dimensional structure of aquaporin-1
    (Nature Publishing Group, 1997-06-05) Engel, Andreas; Agre, Peter; Smith, Barbara L.; Fujiyoshi, Yoshinori; Mitsuoka, Kaoru; Heymann, J. Bernard; Murata, Kazuyoshi; Hirai, Teruhisa; Walz, Thomas
    The entry and exit of water from cells is a fundamental process of life. Recognition of the high water permeability of red blood cells led to the proposal that specialized water pores exist in the plasma membrane. Expression in Xenopus oocytes and functional studies of an erythrocyte integral membrane protein of relative molecular mass 28,000, identified it as the mercury-sensitive water channel, aquaporin-1 (AQP1). Many related proteins, all belonging to the major intrinsic protein (MIP) family, are found throughout nature. AQP1 is a homotetramer containing four independent aqueous channels. When reconstituted into lipid bilayers, the protein forms two-dimensional lattices with a unit cell containing two tetramers in opposite orientation. Here we present the three-dimensional structure of AQP1 determined at 6A resolution by cryo-electron microscopy. Each AQP1 monomer has six tilted, bilayer-spanning alpha-helices which form a right-handed bundle surrounding a central density. These results, together with functional studies, provide a model that identifies the aqueous pore in the AQP1 molecule and indicates the organization of the tetrameric complex in the membrane.
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    Mutations in aquaporin-1 in phenotypically normal humans without functional CHIP water channels
    (American Association for the Advancement of Science, 1994-09-09) Agre, Peter; Moulds, J. J.; Zeidel, ML; Smith, BL; Preston, GM
    The gene aquaporin-1 encodes channel-forming integral protein (CHIP), a member of a large family of water transporters found throughout nature. Three rare individuals were identified who do not express CHIP-associated Colton blood group antigens and whose red cells exhibit low osmotic water permeabilities. Genomic DNA analyses demonstrated that two individuals were homozygous for different nonsense mutations (exon deletion or frameshift), and the third had a missense mutation encoding a nonfunctioning CHIP molecule. Surprisingly, none of the three suffers any apparent clinical consequence, which raises questions about the physiological importance of CHIP and implies that other mechanisms may compensate for its absence.
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    Structural determinants of water permeation through aquaporin-1
    (Nature Publishing Group, 2000-10-05) Fujiyoshi, Yoshinori; Engel, Andreas; Heymann, J. Bernard; Agre, Peter; Walz, Thomas; Hirai, Teruhisa; Mitsuoka, Kaoru; Murata, Kazuyoshi
    Human red cell AQP1 is the first functionally defined member of the aquaporin family of membrane water channels. Here we describe an atomic model of AQP1 at 3.8A resolution from electron crystallographic data. Multiple highly conserved amino-acid residues stabilize the novel fold of AQP1. The aqueous pathway is lined with conserved hydrophobic residues that permit rapid water transport, whereas the water selectivity is due to a constriction of the pore diameter to about 3 A over a span of one residue. The atomic model provides a possible molecular explanation to a longstanding puzzle in physiology-how membranes can be freely permeable to water but impermeable to protons.
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    Rapid gating and anion permeability of an intracellular aquaporin
    (Nature Publishing Group, 1992-11-11) Agre, Peter; Guggino, WB; Nielsen, S; Kwon, TH; Hazama, A.; Yasui, M.
    Aquaporin (AQP) water-channel proteins are freely permeated by water but not by ions or charged solutes. Although mammalian aquaporins were believed to be located in plasma membranes, rat AQP6 is restricted to intracellular vesicles in renal epithelia. Here we show that AQP6 is functionally distinct from other known aquaporins. When expressed in Xenopus laevis oocytes, AQP6 exhibits low basal water permeability; however, when treated with the known water channel inhibitor, Hg2+, the water permeability of AQP6 oocytes rapidly rises up to tenfold and is accompanied by ion conductance. AQP6 colocalizes with H+-ATPase in intracellular vesicles of acid-secreting alpha-intercalated cells in renal collecting duct. At pH less than 5.5, anion conductance is rapidly and reversibly activated in AQP6 oocytes. Site-directed mutation of lysine to glutamate at position 72 in the cytoplasmic mouth of the pore changes the cation/anion selectivity, but leaves low pH activation intact. Our results demonstrate unusual biophysical properties of an aquaporin, and indicate that anion-channel function may now be explored in a protein with known structure.
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    Appearance of Water Channels in Xenopus Oocytes Expressing Red Cell CHIP28 Protein
    (American Association for the Advancement of Science, 1992-04-17) Agre, Peter; Guggino, William B.; Carroll, Tiziana Piazza; Preston, Gregory M.
    Water rapidly crosses the plasma membrane of red blood cells (RBCs) and renal tubules through specialized channels. Although selective for water, the molecular structure of these channels is unknown. The CHIP28 protein is an abundant integral membrane protein in mammalian RBCs and renal proximal tubules and belongs to a family of membrane proteins with unknown functions. Oocytes from Xenopus laevis microinjected with in vitro-transcribed CHIP28 RNA exhibited increased osmotic water permeability; this was reversibly inhibited by mercuric chloride, a known inhibitor of water channels. Therefore it is likely that CHIP28 is a functional unit of membrane water channels.
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    Partial deficiency of erythrocyte spectrin in hereditary spherocytosis.
    (Nature Publishing Group, 1985-03-28) Bennett, Vann; McMillan, Campbell; Casella, James F.; Zinkham, William H.; Agre, Peter
    Hereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the spectrin-actin membrane skeleton, leading to loss of surface membrane. Recessively inherited spectrin deficiency with extreme erythrocyte fragility and spherocytosis has been identified in certain mutant mice and two severely anaemic humans. Although suspected, deficiency of spectrin has not been demonstrated in less severe forms of human HS. We not report the quantitation of erythrocytes spectrin by radioimmunoassay. We found that normal erythrocytes contained 240,000 copies of spectrin heterodimer, whereas erythrocytes from 14 patients with a variety of types of HS were all partially deficient in spectrin (range 74,000-200,000 copies), the magnitude of the deficiency correlating with the severity of the disease. Spectrin deficiency of varying degrees is common in HS and probably represents the principal structural defect leading to loss of surface membrane.
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    Heterotetrameric composition of aquaporin-4 water channels.
    (American Chemical Society, 1999-08-24) Agre, Peter; Nielsen, S; Christensen, B. M.; Neely, JD
    Aquaporin (AQP) water channel proteins are tetrameric assemblies of individually active approximately 30 kDa subunits. AQP4 is the predominant water channel protein in brain, but immunoblotting of native tissues has previously yielded multiple poorly resolved bands. AQP4 is known to encode two distinct mRNAs with different translation initiating methionines, M1 or M23. Using SDS-PAGE urea gels and immunoblotting with anti-peptide antibodies, four polypeptides were identified in brain and multiple other rat tissues with the following levels of expression: 32 kDa > 34 kDa > 36 kDa > 38 kDa. The 34 and 38 kDa polypeptides react with an antibody specific for the N-terminus of the M1 isoform, and 32 and 36 kDa correspond to the shorter M23 isoform. Immunogold electron microscopic studies with rat cerebellum cryosections demonstrated that the 34 kDa polypeptide colocalizes in perivascular astrocyte endfeet where the 32 kDa polypeptide is abundantly expressed. Velocity sedimentation, cross-linking, and immunoprecipitation analyses of detergent-solubilized rat brain revealed that the 32 and 34 kDa polypeptides reside within heterotetramers. Immunoprecipitation of AQP4 expressed in Xenopus laevis oocytes demonstrated that heterotetramer formation reflects the relative expression levels of the 32 and 34 kDa polypeptides; however, tetramers containing different compositions of the two polypeptides exhibit similar water permeabilities. These studies demonstrate that AQP4 heterotetramers are formed from two overlapping polypeptides and indicate that the 22-amino acid sequence at the N-terminus of the 34 kDa polypeptide does not influence water permeability but may contribute to membrane trafficking or assembly of arrays.
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    Reconstitution of functional water channels in liposomes containing purified red cell CHIP28 protein
    (American Chemical Society, 1992) Agre, Peter; Smith, Barbara L.; Ambudkar, Suresh V.; Zeidel, Mark L.
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    Inheritance pattern and clinical response to splenectomy as a reflection of erythrocyte spectrin deficiency in hereditary spherocytosis
    (Massachusetts Medical Society, 1986-12-18) Asimos, Andrew; Agre, Peter; McMillan, Campbell; Casella, James F.
    To determine how various inheritance patterns and responses to splenectomy relate to erythrocyte spectrin deficiencies in hereditary spherocytosis, we measured the spectrin content of erythrocytes by radioimmunoassay in 33 patients with this disease. Patients with the dominant form of hereditary spherocytosis generally had mild anemia, with spectrin at 63 to 81 percent of normal levels. Patients with the nondominant form of the disease had anemia ranging from severe to mild, with corresponding spectrin levels of 30 to 74 percent; their siblings were affected similarly. Distantly related homozygotes had different clinical severities with correspondingly different spectrin levels. The parents and offspring of patients with the nondominant form were clinically normal but consistently had subtle erythrocyte abnormalities. Spectrin levels in all patients were inversely related to osmotic fragility (P less than 0.0001), and they were also correlated with the clinical response to splenectomy: patients with spectrin levels above 70 percent achieved normal blood counts, those with levels of 40 to 70 percent had compensated hemolysis, and those with levels below 40 percent improved but remained anemic (P less than 0.0001). We conclude that the inheritance pattern and response to splenectomy in hereditary spherocytosis reflect erythrocyte spectrin deficiencies as determined by radioimmunoassay.
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    Deficient red-cell spectrin in severe, recessively inherited spherocytosis
    (Massachusetts Medical Society, 1982-05-13) Agre, Peter; Bennett, Vann; Orringer, Eugene P.
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    The Rh polypeptide is a major fatty acid-acylated erythrocyte membrane protein
    (American Society for Biochemistry and Molecular Biology, 1988-12-05) Agre, Peter; de Vetten, Marcel P
    The erythrocyte Rh antigens contain an Mr = 32,000 integral protein which is thought to contribute in some way to the organization of surrounding phospholipid. To search for possible fatty acid acylation of the Rh polypeptide, intact human erythrocytes were incubated with [3H]palmitic acid prior to preparation of membranes and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Several membrane proteins were labeled, but none corresponded to the glycophorins or membrane proteins 1-8. An Mr = 32,000 band was prominently labeled on Rh (D)-negative and -positive erythrocytes and could be precipitated from the latter with anti-D. No similar protein was labeled on membranes from Rhmod erythrocytes, a rare phenotype lacking Rh antigens. Labeling of the Rh polypeptide most likely represents palmitic acid acylation through thioester linkages. The 3H label was not extracted with chloroform/methanol, but was quantitatively eluted with hydroxylamine and co-chromatographed with palmitohydroxamate and free palmitate by thin layer chromatography. The fatty acid acylations occurred independent of protein synthesis and were completely reversed by chase with unlabeled palmitate. It is concluded that the Rh polypeptide is fatty acid-acylated, being a major substrate of an acylation-deacylation mechanism associated with the erythrocyte membrane.
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    Water and ion permeation of aquaporin-1 in planar lipid bilayers. Major differences in structural determinants and stoichiometry.
    (American Society for Biochemistry and Molecular Biology, 2001-08-24) Pohl, Peter; Agre, Peter; Rothe, Ulrich; Kozono, David; Saparov, S. M.
    The aquaporin-1 (AQP1) water channel protein is known to facilitate the rapid movement of water across cell membranes, but a proposed secondary role as an ion channel is still unsettled. Here we describe a method to simultaneously measure water permeability and ion conductance of purified human AQP1 after reconstitution into planar lipid bilayers. Water permeability was determined by measuring Na(+) concentrations adjacent to the membrane. Comparisons with the known single channel water permeability of AQP1 indicate that the planar lipid bilayers contain from 10(6) to 10(7) water channels. Addition of cGMP induced ion conductance in planar bilayers containing AQP1, whereas cAMP was without effect. The number of water channels exceeded the number of active ion channels by approximately 1 million-fold, yet p-chloromethylbenzenesulfonate inhibited the water permeability but not ion conductance. Identical ion channel parameters were achieved with AQP1 purified from human red blood cells or AQP1 heterologously expressed in Saccharomyces cerevisae and affinity purified with either N- or C-terminal poly-histidine tags. Rp-8-Br-cGMP inhibited all of the observed conductance levels of the cation selective channel (2, 6, and 10 pS in 100 mm Na(+) or K(+)). Deletion of the putative cGMP binding motif at the C terminus by introduction of a stop codon at position 237 yielded a truncated AQP1 protein that was still permeated by water but not by ions. Our studies demonstrate a method for simultaneously measuring water permeability and ion conductance of AQP1 reconstituted into planar lipid bilayers. The ion conductance occurs (i) through a pathway distinct from the aqueous pathway, (ii) when stimulated directly by cGMP, and (iii) in only an exceedingly small fraction of AQP1 molecules.
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    Functional expression and characterization of an archaeal aquaporin. AqpM from methanothermobacter marburgensis.
    (American Society for Biochemistry and Molecular Biology, 2003-03-21) Kitagawa, Yoshichika; Agre, Peter; Kamagato, Yoichi; Meng, Xianying; Iwasaki, Ikuko; Ding, Xiaodong; Kozono, David
    Researchers have described aquaporin water channels from diverse eubacterial and eukaryotic species but not from the third division of life, Archaea. Methanothermobacter marburgensis is a methanogenic archaeon that thrives under anaerobic conditions at 65 °C. After transfer to hypertonic media,M. marburgensis sustained cytoplasmic shrinkage that could be prevented with HgCl2. We amplified aqpM by PCR from M. marburgensis DNA. Like known aquaporins, the open reading frame of aqpM encodes two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Unlike other known homologs, the putative Hg2+-sensitive cysteine was found proximal to the first NPA motif in AqpM, rather than the second. Moreover, amino acids distinguishing water-selective homologs from glycerol-transporting homologs were not conserved in AqpM. A fusion protein, 10-His-AqpM, was expressed and purified from Escherichia coli. AqpM reconstituted into proteoliposomes was shown by stopped-flow light scattering assays to have elevated osmotic water permeability (P f = 57 μm·s−1 versus12 μm·s−1 of control liposomes) that was reversibly inhibited with HgCl2. Transient, initial glycerol permeability was also detected. AqpM remained functional after incubations at temperatures above 80 °C and formed SDS-stable tetramers. Our studies of archaeal AqpM demonstrate the ubiquity of aquaporins in nature and provide new insight into protein structure and transport selectivity. To withstand environmental and physiological stresses, organisms must be able to rapidly absorb and release water. Facilitated transport of water across cell membranes must be highly selective to prevent uncontrolled movement of other solutes, protons, and ions. Discovery of the aquaporins provided a molecular explanation to these processes (2). More than 200 aquaporins have now been identified, and their presence has been established in most forms of life (3). No aquaporin from Archaea has yet been characterized, although functional roles for a water channel protein have been predicted in these organisms (4). Two major protein family subsets are presently recognized, water-selective channels (aquaporins) and glycerol-transporting homologs with varying water permeabilities (aquaglyceroporins). The permeation selectivity of new members of the protein family may be predicted by a small number of conserved residues (5, 6). Several prokaryotic aquaporins and aquaglyceroporins are known. The bacterial water channel, AqpZ, was first identified in Escherichia coli (7, 8). Movement of water across the bacterial plasma membrane may be part of the osmoregulatory response by which microorganisms adjust cell turgor (9), although the regulation and physiological role of AqpZ are being reassessed (10). AqpZ is a highly stable tetramer with negligible permeability to glycerol. In contrast, the glycerol permeability of the glycerol facilitator (GlpF) fromE. coli has long been recognized (11). GlpF has relatively limited water permeability (12), and the tetrameric form has reduced stability in some detergents (13). Atomic resolution structures have been solved for GlpF (14) as well as human and bovine AQP11 (15-17). These have elucidated differential specificities and functional mechanisms of the two sequence-related proteins. Archaea and certain other microorganisms are able to withstand exceptional challenges in maintaining water balance as they thrive in extreme environments including saturated salt solutions, extreme pH, and temperatures up to 130 °C (18). We recently recognized the DNA sequence of AqpM, a candidate aquaporin or aquaglyceroporin in the genome of a methanogenic thermophilic archaeon,Methanothermobacter marburgensis 2 (,19). Here we investigate water permeability in living cells and report the purification, functional reconstitution, and characterization of AqpM.
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    Characterization of aquaporin-6 as a nitrate channel in mammilian cells: Requirement of pore-lining residue threonine 63
    (American Society for Biochemistry and Molecular Biology, 2002-10-18) Yasui, Masato; Agre, Peter; Guggino, William B.; Kozono, David; Beitz, Eric; Ikeda, Masahiro
    Aquaporins (AQP) were originally regarded as plasma membrane channels that are freely permeated by water or small uncharged solutes but not by ions. Unlike other aquaporins, AQP6 overexpressed in Xenopus laevis oocytes was previously found to exhibit Hg2+ or pH-activated ion conductance. AQP6 could not be analyzed electrophysiologically in mammalian cells, however, because the protein is restricted to intracellular vesicles. Here we report that addition of a green fluorescence protein (GFP) tag to the N terminus of rat AQP6 (GFP-AQP6) redirects the protein to the plasma membranes of transfected mammalian cells. This permitted measurement of rapid, reversible, pH-induced anion currents by GFP-AQP6 in human embryonic kidney 293 cells. Surprisingly, anion selectivity relative to Cl- revealed high nitrate permeability even at pH 7.4; P(NO3)/P(Cl) > 9.8. Site-directed mutation of a pore-lining threonine to isoleucine at position 63 at the midpoint of the channel reduced NO3-/Cl- selectivity. Moreover, no anomalous mole-fraction behavior was observed with NO3-/Cl- mixtures, suggesting a single ion-binding pore in each subunit. Our studies indicate that AQP6 exhibits a new form of anion permeation with marked specificity for nitrate conferred by a specific pore-lining residue, observations that imply that the primary role of AQP6 may be in cellular regulation rather than simple fluid transport.