Cataractogenesis in Transgenic Mice Containing the HIV-1 Protease Linked to the Lens αA-Crystallin Promoter

Abstract

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.

Lens Crystallin Modifications and Cataract in Transgenic Mice Overexpressing Acylpeptide Hydrolase

“…Our observations of APH and cataract development are similar to those described in the previously reported studies of transgenic mice expressing HIV-1 protease in the lens under the control of ␣A-crystallin promoter (40). Mice with active HIV-1 protease developed cataract, and mice bearing inactive protease had normal lens.…”

“…Proteolysis of crystallins is known to occur in nonhuman lenses during aging (29 -32) and in animal models of cataract (33)(34)(35)(36). Extensive studies of calpain, including Lp82 (37)(38)(39), and of transgenic mice expressing the HIV protease (40) have confirmed that proteolysis of crystallins is one of the factors in cataract formation. However, unlike in rodent cataract, lensspecific calpain Lp82 has not been found to be involved in human cataractogenesis and, because HIV protease is foreign to the lens, other proteases are responsible for the proteolysis in human agerelated cataract lenses and diabetic lenses.…”

Cysteine Protease Activated by Expression of HIV-1 Protease in Transgenic Mice

“…3). The 25-kDa and 23-kDa bands only displayed reactivity to the N-terminal directed anti-MIP- (1)(2)(3)(4)(5)(6)(7)(8). Degradation of the MIP26 in organ culture was from the C terminus and mimicked the degradation in vivo.…”

“…Cataract formation is dependent on the HIV-1 protease, because transgenic mice expressing an inactive HIV-1 protease in the lens remain cataract-free as do TG 72 mice that are administered HIV-1 protease inhibitors (6). In homozygous TG 72 mice, lenses show refractive index changes prior to cataract formation.…”

Congenital nuclear cataracts and uveitis in HIV-transgenic mice

“…More recently, cataracts have been described in mice transgenic for the HIV-1 protease under the control of the lens alpha A-crystallin promoter. 15,16 The authors concluded that proteolysis of lens proteins, presumably induced by the viral protease, was responsible for cataract formation. Most recently, Dickie 17 reported on cataracts occurring in five transgenic lines of mice derived from four constructs: intact HIV-1 proviral DNA under the control of the HIV-1 long terminal repeat (LTR) or a chimeric HIV-1/MMTV LTR, a gag-pol deleted genome and the Nef gene.…”