Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.24.59 (MIP)
4,906 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cDNA for the fifth mammalian aquaporin (AQP5) was isolated from rat, and expression was demonstrated in rat salivary and lacrimal glands, cornea, and lung (Raina, S., Preston, G. M., Guggino, W. B., and Agre, P. (1995) J. Biol. Chem. 270, 1908-1912). Here we report the isolation and characterization of the human AQP5 cDNA and gene. The AQP5 cDNA from a human submaxillary gland library contains a 795-base pair open reading frame encoding a 265-amino acid protein. The deduced amino acid sequences of human and rat AQP5 are 91% identical with 6 substitutions in the 22-amino acid COOH-terminal domain. Expression of human AQP5 in Xenopus oocytes conferred mercurial-sensitive osmotic water permeability (Pf) equivalent to other aquaporins. The human AQP5 structural gene resides within a 7. 4-kilobase SalI-EcoRI fragment with four exons corresponding to amino acids 1-121, 122-176, 177-204, and 205-265 separated by introns of 1.2, 0.5, and 0.9 kilobases. A transcription initiation site was identified 518 base pairs upstream of the initiating methionine. Genomic Southern analysis indicated that AQP5 is a single copy gene which localized to human chromosome 12q13; this coincides with the chromosomal locations of the homologous human genes MIP and AQP2, thus confirming 12q13 as the site of an aquaporin gene cluster. The mouse gene localized to distal chromosome 15. This information may permit molecular characterization of AQP5 expression during normal development and in clinical disorders.
...
PMID:The human Aquaporin-5 gene. Molecular characterization and chromosomal localization. 862 89

Xenopus laevis oocytes are widely used as an expression system for plasma membrane proteins, achieved by cytoplasmic microinjection of messenger RNA. In the present study, we propose an alternative system allowing functional insertion of exogenous proteins into the plasma membrane of Xenopus oocytes. We microinjected proteoliposome suspensions into the cytoplasm and then analyzed membrane protein function. The proteins used in this work were members of the MIP family: the human erythrocyte water channel aquaporin 1 (AQP1), the major intrinsic protein (MIP26) from bovine eye lens and a 25 kDa polypeptide (P25) from a water shunting complex found in the digestive tract of an homopteran sap-sucking insect (Cicadella viridis). Proteoliposomes containing either AQP1, MIP26, or P25 were injected into Xenopus oocytes. The subsequent insertion of these proteins into the plasma membrane of oocytes was demonstrated by immunocytochemistry. Oocytes microinjected with either AQP1 or P25-proteoliposomes exhibited significantly increased osmotic membrane water permeabilities (Pf = 3.16 +/- 026 and 4.03 +/- 0.26 x 10(-3) cm/second, respectively) compared to those measured for oocytes injected with liposomes alone or with MIP26-proteoliposomes (Pf = 1.39 +/- 0.07 and 1.44 +/- 0.10 x 10(-3) cm/second, respectively). These effects were inhibited by HgCl2 in a reversible manner. Arrhenius activation energies of water transfer were low when AQP1 or P25 were present in oocyte plasma membranes (Ea = 2.29 and 3.01 kcal/mol, respectively, versus Ea = 11.75 kcal/mol for liposome injected oocytes). The properties observed here for AQP1 are identical to those widely reported following AQP1 cRNA expression in oocytes. From the present study, we conclude that: (1) exogenous plasma membrane proteins incorporated into liposomes and microinjected into the cytoplasm of Xenopus oocytes are subsequently found in the plasma membrane of the oocytes in a functional state; and (2) in this system, the P25 polypeptide from the MIP family found in the digestive tract of Cicadella viridis exhibits properties similar to those described for the archetype of water channels AQP1, and thus is a new member of the aquaporin family.
...
PMID:Incorporation of proteins into (Xenopus) oocytes by proteoliposome microinjection: functional characterization of a novel aquaporin. 879 18

Transgenic mice, homozygous for HIV-1 protease expression in the eye lens, display degradation of some lens crystallins and cytoskeletal proteins prior to cataract formation on postnatal days 23-25. Alterations to the internal lens hydration state also occur; therefore, the status of the aquaporin protein MIP26 was examined over postnatal days 16-25 to determine if it was altered during cataractogenesis. The MIP was identical in transgenic and control lenses until day 21. By postnatal day 25 (frank cataract), in the lenses obtained from transgenic animals, the 26-kDa band was absent and there was a concurrent increase in the proportion of MIP23. Immunoblotting demonstrated cleavage at the C terminus. Lenses were also maintained in an organ culture system to demonstrate that the cataractogenic process is inherent to the isolated lens and to determine the contribution of cysteine protease action. Organ culture experiments revealed a similar progression to nuclear cataract formation as seen in vivo. Two-dimensional gel analysis of the soluble lens crystallin fraction of organ cultured lenses revealed the same cleavage pattern as occurs in vivo. Organ culture of transgenic lenses with E64, a cysteine protease inhibitor, dramatically delayed cataractogenesis and prevented proteolytic cleavage of both MIP26 and crystallins. HIV-1 protease, while the trigger of cataract formation, does not appear to be the protease responsible for cleavage of MIP or lens crystallins. These results suggest that activation of endogenous cysteine protease activity is involved in the cleavage of these proteins and occurs downstream of HIV-1 protease action.
...
PMID:Cysteine protease activated by expression of HIV-1 protease in transgenic mice. MIP26 (aquaporin-0) cleavage and cataract formation in vivo and ex vivo. 894 20

A new member of the aquaporin (AQP) family has been identified from rat testis. This gene, referred as aquaporin 7 (AQP7), encodes a 269-amino acid protein that contained the conserved NPA motifs of MIP family proteins. AQP7 has the amino acid sequence homology with other aquaporins ( approximately 30%), and it is highest with AQP3 (48%), suggesting that both AQP3 and AQP7 belong to a subfamily in the MIP family. Injection of AQP7-cRNA into Xenopus oocytes expressed a 26-kDa protein detected by immunoblotting. The expression of AQP7 in oocytes stimulated the osmotic water permeability by 10-fold which was not inhibited by 0.3 mM mercury chloride. The Arrhenius activation energy for the stimulated water permeability was low (2.1 kcal/mol). AQP7 also facilitated glycerol and urea transport by 5- and 9-fold, respectively. The activation energy for glycerol was also low (5.3 kcal/mol after the correction of the endogenous glycerol permeability of oocytes). Northern blot analysis revealed a 1.5-kilobase pair transcript expressed abundantly in testis. In situ hybridization of testis revealed the expression of AQP7 at late spermatids in seminiferous tubules. The immunohistochemistry of testis localized the AQP7 expression at late spermatids and at maturing sperms. AQP7 may play an important role in sperm function.
...
PMID:Cloning and functional expression of a new water channel abundantly expressed in the testis permeable to water, glycerol, and urea. 925 1

An aquaporin-type water channel was isolated from mouse based on homology to known aquaporins. A 1447 bp cDNA was sequenced (designated AQP8) with a 783 bp open reading frame encoding a 261 amino acid hydrophobic protein which contained the conserved NPA motifs of MIP family members. Amino acid alignment showed greatest homology of AQP8 to plant water channel gamma TIP (38% identity) followed by mammalian water channels AQP4 (32%) and AQP2 (31%). Northern blot analysis indicated a 1.7 kb transcript expressed strongly in placenta > colon > liver approximately heart. RT-PCR with AQP8-specific primers and Southern blot analysis showed AQP8 transcript in the above tissues and in pancreas, lung, kidney, submandibular gland, diaphragm, testis, spleen, stomach and brain. Expression of AQP8 cRNA in Xenopus oocytes increased osmotic water permeability from (0.8 +/- 0.1) x 10(-3) cm/s to (22 +/- 3) x 10(-3) cm/s (10 degrees C) in a mercurial-sensitive manner. AQP8 was also permeable to urea but not to glycerol. Normalization for oocyte plasma membrane expression using cMyc-tagged AQP8 indicated a single channel water permeability of 8.2 x 10(-14) cm3/s. AQP8 is unique among the water channels in terms of its urea permeability and its strong expression in gastrointestinal organs, placenta and heart.
...
PMID:Cloning of a novel water and urea-permeable aquaporin from mouse expressed strongly in colon, placenta, liver, and heart. 938 76

Since 1992 and the discovery of an MIP (major intrinsic protein of lens fiber cell) homologue protein that selectively permeates water, aquaporin (AQP), there has been an explosion of research in this field. Early research speculated that aquaporins played indispensible physiological roles in bacteria and plants, as well as in mammalian organs such as red blood cells, kidney, eye, brain and lung, where water transport rapidly takes place. Yet human subjects were identified who lacked AQP1 and yet had no apparent phenotypical changes clinically. To date 10 aquaporins have been discovered and a plethora of MIP members, and their prevalance in almost all organisms is a testament to their indispensible roles in the body, possibly as water and small neutral solute transporting channels. The recent localization of many different aquaporins in the same organ indicates that they may work cooperatively, which may partially explain the mystery of their physiological mechanism. Because the physiological roles of most aquaporins are currently only speculation, more extensive research is necessary to understand the exact function of each aquaporin.
...
PMID:Aquaporins in the kidney: emerging new aspects. 976 20

The MIP (major intrinsic protein) proteins constitute a channel family of currently 150 members that have been identified in cell membranes of organisms ranging from bacteria to man. Among these proteins, two functionally distinct subgroups are characterized: aquaporins that allow specific water transfer and glycerol channels that are involved in glycerol and small neutral solutes transport. Since the flow of small molecules across cell membranes is vital for every living organism, the study of such proteins is of particular interest. For instance, aquaporins located in kidney cell membranes are responsible for reabsorption of 150 liters of water/day in adult human. To understand the molecular mechanisms of solute transport specificity, we analyzed mutant aquaporins in which highly conserved residues have been substituted by amino acids located at the same positions in glycerol channels. Here, we show that substitution of a tyrosine and a tryptophan by a proline and a leucine, respectively, in the sixth transmembrane helix of an aquaporin leads to a switch in the selectivity of the channel, from water to glycerol.
...
PMID:Switch from an aquaporin to a glycerol channel by two amino acids substitution. 1006 30

A gene fragment encoding a putative member of the aquaporin gene family was amplified using cDNA prepared from unfed adult buffalo fly poly(A)+ RNA and degenerate PCR primers designed from highly conserved regions of amino acids found in all members of the aquaporin gene family. This PCR product was labelled with digoxigenin-dUTP and used as a probe to screen a lambdagt-11 cDNA library constructed from unfed adult buffalo fly. One positively hybridizing clone (AqpBF1), contained an insert of 1878 bp, and DNA sequence analysis revealed an open reading frame of 753 bp encoding a polypeptide of predicted Mr = 26 163 Da. Comparison of the AqpBF1 deduced protein sequence with the GenBank database revealed significant homology to many aquaporin genes, including 72% identity with a partial DNA sequence encoding a member (DRIP) of the MIP protein family isolated from Drosophila melanogaster. The most closely related, full-length, GenBank sequence was an aquaporin gene isolated from the digestive tract of the sap-sucking insect Cicadella viridis, which was 53% identical to the buffalo fly AqpBF1 protein sequence. The full-length coding sequence of AqpBF1 was cloned into the (His)6-fusion vector, pQE10, and the recombinant protein was expressed in Escherichia coli following induction by IPTG. The recombinant (His)6-fusion protein was localized predominantly in the membrane fraction of E. coli. The protein was solubilized from E. coli membranes with n-octyl beta-D-glucopyranoside and purified by affinity chromatography on a Ni++-sepharose column in the presence of detergent.
...
PMID:Molecular cloning and expression in Escherichia coli of an aquaporin-like gene from adult buffalo fly (Haematobia irritans exigua). 1046 54

The MIP (major intrinsic protein) family is a widespread family of membrane proteins exhibiting two major types of channel properties: aquaporins and solute facilitators. In the present study, freeze-fracture electron microscopy was used to investigate the oligomerization state of two MIP proteins heterologously expressed in the plasma membrane of Xenopus laevis oocytes: AQPcic, an aquaporin from the insect Cicadella viridis, and GlpF, a glycerol facilitator from Escherichia coli. Swelling assays performed on oocytes 48 and 72 h following cRNA microinjections showed that these proteins were functionally expressed. Particle density determinations indicated that expression of proteins is related to an increase in particle density on the P fracture face of oocyte plasma membranes. Statistical analysis of particle sizes was performed on protoplasmic fracture faces of the plasma membrane of oocytes expressing AQPcic and GlpF 72 h after cRNA microinjections. Compared to control oocytes, AQPcic-expressing oocytes exhibited a specific population of particles with a mean diameter of 8.7 +/- 0.1 nm. This value is consistent with the previously reported tetrameric organization of AQPcic. In addition, AQPcic particles aggregate and form orthogonal arrays similar to those observed in native membranes of C. viridis, consisting of homotetramers of AQPcic. On the protoplasmic fracture face of oocytes expressing GlpF, the particle density is increased by 4.1-fold and the mean diameter of specifically added particles is 5.8 +/- 0.1 nm. This value fits with a monomer of the 28-kDa GlpF protein plus the platinum-carbon layer. These results clearly demonstrate that GlpF is a monomer when functionally expressed in plasma membranes of Xenopus oocytes and therefore emphasize the key role of the oligomerization state of MIP proteins with respect to their function.
...
PMID:Oligomerization state of MIP proteins expressed in Xenopus oocytes as revealed by freeze-fracture electron-microscopy analysis. 1063 68

Human inherited cataract is both clinically diverse and genetically heterogeneous. Here we report the identification of the first mutations affecting the major intrinsic protein of the lens, MIP, encoded by the gene MIP on 12q14. MIP is a member of the aquaporin family of membrane-bound water channels. The mutations identified are predicted to disturb water flux across the lens cell membrane.
...
PMID:Missense mutations in MIP underlie autosomal dominant 'polymorphic' and lamellar cataracts linked to 12q. 1080 46


1 2 3 Next >>

---