Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.23.16 (HIV-1 protease)
 2,107 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several lines of transgenic mice were generated with either active or inactive forms of the human immunodeficiency virus type 1 (HIV-1) protease gene under the control of the mouse lens alpha A-crystallin promoter. Mice bearing the inactive protease coding sequence displayed no gross abnormalities in the lens, while mice with the active protease developed time-dependent bilateral cataracts. One line, TG61, developed cataracts in utero while the second line, TG72, developed cataracts postnatally. TG61 mice, homozygous for the transgene, developed severe microphthalmia and were significantly smaller than the control mice at postnatal day 30. two-dimensional-polyacrylamide gel electrophoresis analysis of the protein profiles of TG72 and TG61 lenses revealed extensive modifications in the lens crystallins. Proteolysis in the homozygous TG72 mouse lenses began at postnatal day 20 with the disappearance or partial loss of beta B1-, beta B3-, and beta A3-crystallins and the appearance of crystallin fragments. Protein leakage and the gradual breakdown of cytoskeletal elements also occurred. In contrast, the opacification of the homozygous TG61 lenses appeared to have been influenced by differentiation and developmental processes. It appears that HIV-1 protease expression activates other proteases, and these enzymes, in concert with HIV-1 protease, are responsible for the protein modifications that eventually result in the opacification of the lens.
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PMID:Cataractogenesis in transgenic mice containing the HIV-1 protease linked to the lens alpha A-crystallin promoter. 855 May 98

Two constructs of transgenic mice, TG61 and TG72, containing HIV-1 protease linked to lens alpha A-crystallin promoter develop cataract. The TG61 construct exhibits cataractogenesis in utero, while in the TG72 construct frank opacities appear 24 days (homozygotes) and 26 days (hemizygotes) after birth. Differential scanning calorimetry and thermogravimetric analysis studies indicate that the hydration of lenses is strongly correlated with cataractogenesis. In all clear lenses (normal and precataractous) the total water content was the same, 68%, and increased upon opacification. The bound water, measured as percentage nonfreezable water of the total water, decreased upon cataract formation, indicating a syneretic process. On the other hand, the bound water expressed as grams of nonfreezable water per gram dry weight increases upon opacification. This implies that proteolysis and subsequent enhanced hydration is the primary supramolecular event in cataractogenesis and that syneresis in the lens of transgenic mice is of secondary importance.
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PMID:Lens hydration in transgenic mice containing HIV-1 protease linked to the lens alpha A-crystallin promoter. 855 13

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.
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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

Two constructs of transgenic mice, TG61 and TG72, containing the HIV-1 protease linked to the lens alpha A-crystallin promoter develop cataract. The TG61 construct develop cataract in utero, while the TG72 construct exhibit frank opacities on the 24th day (homozygotes) and 26th day (hemizygotes) post natum. Polarized light scattering measurements were performed on cortical and nuclear sections of TG72 lenses from day 19 to day 26 as a function of scattering angle. The parallel components of the scattered light intensity increase gradually during opacification, the perpendicular components show very low values from day 19 to day 22 after which they increase exponentially. Analysis of the scattered light intensities yielded parameters describing the size of the protein aggregates, the size of the domains exhibiting optical anisotropy/birefringence, the difference in refractive index between (a) the protein aggregates and their surroundings and (b) the birefringent units and their surroundings. The last parameter accounts for the major portion of the increase in lens turbidity. The TG72 construct shows normal lens development on day 16. By day 21 the posterior cortex shows some disintegration, while the lens is still clear. By day 26 the lens nucleus migrates toward the posterior pole and there is a major alteration in the cortical fibers. Scanning electron microscopic studies reveal normal fiber cell organizations in control animals. In the TG72 construct the fiber cells are well organized at 16 days after birth but already develop some slight separation in the posterior cortical part of the lens. By post-natal day 21, the nucleus and the anterior cortex still exhibit well aligned fiber cell organization, but the posterior cortex shows disalignment. By day 26 in the TG72 construct, all areas of the lens show complete disintegration of the fiber cells and amorphous masses are present throughout. The light scattering parameters describing changes on the nanometer scale can be correlated with the changes in lens morphology during cataractogenesis that occur on the micrometer scale. In comparison, the light and scanning electron microscopic examinations of the postnatal TG61 construct show that the lens is severely disrupted and contains completely disintegrated fiber cell remnants at an early age.
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PMID:Light scattering and morphology of cataract formation in transgenic mice containing the HIV-1 protease linked to the lens alpha A-crystallin promoter. 924 95

Scanning electron microscopy of the lenses from transgenic mice (TG(72)) containing the HIV-1 protease linked to the lens alphaA-crystallin promoter showed structural changes around postnatal day 16. Frank opacification of the lens was observed at day 24. To relate the biochemical and biophysical changes that occur during the process of cataract development, high-resolution two-dimensional gel electrophoresis (2D), quantitative image analysis and ion measurements were carried out on lenses from postnatal day 10 and on days 15-24. The phase separation temperature (Tc), a measure of molecular interactions between proteins, was also determined for normal and transgenic lenses. A comparison of the transgenic and normal lenses on day 10 revealed no significant differences in any of the measured parameters. However, starting around day 16 or the first stage of observed structural changes, the TG(72)crystallin profiles of the alphaA- alphaB-, betaA3-, betaA4-, betaB3 and one gamma-crystallin began to deviate from the normal. By postnatal day 20, a second stage was initiated with an influx of calcium and sodium ions that was accompanied by modifications of betaB1- and betaB2-crystallin. In the third and final stage of the cataract process, a large increase in the proteolysis of crystallins was accompanied by the appearance of the frank cataract on day 24. The Tc initially increased in all of the mouse lenses until just prior to eyelid opening. After that time, the Tc decreased in all lenses. Although the Tc continued to decrease in the normal lenses with age, for the homozygous transgenic mice it exhibited a dramatic increase that began on day 20. Thus, in the TG(72)transgenic mouse, cataract formation occurs in a three-stage process. Tc and other biophysical parameters previously measured appeared to be insensitive to the modifications that occur during stage 1. However, during the second stage of cataract formation, there was a correspondence between abnormal Tc and the abnormal interactions between cellular constituents apparently resulting from lens hydration, the loss of ion homeostasis and continued proteolysis. The last stage of cataract formation results in a total loss of lens transparency and leakage of lens proteins.
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PMID:Three distinct stages of lens opacification in transgenic mice expressing the HIV-1 protease. 1116 27

The folding of HIV-1 protease to its active form involves the coordination of structure formation and dimerization, which follows a hierarchy consisting of folding nuclei spanning from the active site, hinge region, and dimerization domain. However, the biochemical characteristics of the folding intermediates of this protein remain to be elucidated. In an experimental model, the denaturation of the tethered dimer of HIV-1 protease by guanidine hydrochloride revealed an alternative conformation resembling the molten-globule state. The molten-globule state binds to the molecular chaperone alpha-crystallin and prevents its aggregation; however, the chaperone alone failed to reconstitute HIV-1 protease into its active form. Calcium ion assisted in the release of active enzyme from the chaperone complex. Alpha-crystallin, a member of the small heat-shock protein, assists proteins to fold correctly; however, the underlying principle of signals responsible for chaperone-mediated protein folding remains enigmatic. X-ray photoelectron spectroscopy has been employed to provide the evidence of calcium binding to alpha-crystallin and to decipher the effect of calcium binding on the chaperone-mediated refolding of HIV-1 protease. On the basis of our spectroscopic data, we propose that calcium ions interact with the carboxyl groups of the surface-exposed acidic amino acids of alpha-crystallin bringing electrostatic interference, which plays a pivotal role in inducing conformational changes in the chaperone responsible for the release of the active enzyme.
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PMID:Illustration of HIV-1 protease folding through a molten-globule-like intermediate using an experimental model that implicates alpha-crystallin and calcium ions. 1575 49