560 research outputs found
Localization of the Functional Domains of Human Tissue Inhibitor of Metalloproteinases-3 and the Effects of a Sorsby's Fundus Dystrophy Mutation
A transient COS-7 cell expression system was used to
investigate the functional domain arrangement of tissue
inhibitor of metalloproteinases-3 (TIMP-3), specifically
to assess the contribution of the amino- and carboxylterminal
domains of the molecule to its matrix metalloproteinase
(MMP) inhibitory and extracellular matrix
(ECM) binding properties. Wild type TIMP-3 was entirely
localized to the ECM in both its glycosylated (27
kDa) and unglycosylated (24 kDa) forms. A COOH-terminally
truncated TIMP-3 molecule was found to be a non-
ECM bound MMP inhibitor, whereas a chimeric TIMP
molecule, consisting of the NH2-terminal domain of
TIMP-2 fused to the COOH-terminal domain of TIMP-3,
displayed ECM binding, albeit with a lower affinity than
the wild type TIMP-3 molecule. Thus the functional domain
arrangement of TIMP-3 is analogous to that seen in
TIMP-1 and -2, namely that the NH2-terminal domain is
responsible for MMP inhibition whereas the COOH-terminal
domain is most important in mediating the specific
functions of the molecule. A mutant TIMP-3 in
which serine 181 was changed to a cysteine, found in
Sorsby’s fundus dystrophy, a hereditary macular degenerative
disease, was also expressed in COS-7 cells. This
gave rise to an additional 48-kDa species (possibly a
TIMP-3 dimer) that retained its ability to inhibit MMPs
and localize to the ECM. These data favor the hypothesis
that the TIMP-3 mutations seen in Sorsby’s fundus dystrophy
contribute to disease progression by accumulation
of mutant protein rather than by the loss of functional
TIMP-3
A novel tissue inhibitor of metalloproteinases-3 mutation reveals a common molecular phenotype in sorsby's fundus dystrophy
Sorsby’s fundus dystrophy (SFD) is a dominantly inherited
degenerative disease of the retina that leads to
loss of vision in middle age. It has been shown to be
caused by mutations in the gene for tissue inhibitor of
metalloproteinases-3 (TIMP-3). Five different mutations
have previously been identified, all introducing an extra
cysteine residue into exon 5 (which forms part of the
C-terminal domain) of the TIMP-3 molecule; however,
the significance of these mutations to the disease phenotype
was unknown. In this report, we describe the
expression of several of these mutated genes, together
with a previously unreported novel TIMP-3 mutation
from a family with SFD that results in truncation of
most of the C-terminal domain of the molecule. Despite
these differences, all of these molecules are expressed
and exhibit characteristics of the normal protein, including
inhibition of metalloproteinases and binding to
the extracellular matrix. However, unlike wild-type
TIMP-3, they all form dimers. These observations, together
with the recent finding that expression of TIMP-3
is increased, rather than decreased, in eyes from patients
with SFD, provides compelling evidence that
dimerized TIMP-3 plays an active role in the disease
process by accumulating in the eye. Increased expression
of TIMP-3 is also observed in other degenerative
retinal diseases, including the more severe forms of agerelated
macular degeneration, the most common cause
of blindness in the elderly in developed countries. We
hypothesize that overexpression of TIMP-3 may prove to
be a critical step in the progression of a variety of degenerative
retinopathies
Clinical features of a novel TIMP-3 mutation causing Sorsby's fundus dystrophy: implications for disease mechanism
AIMS: To describe the phenotype in three family members affected by a novel mutation in the gene coding for the enzyme tissue inhibitor of metalloproteinase-3 (TIMP-3).
METHODS: Three members of the same family were seen with a history of nyctalopia and visual loss due to maculopathy. Clinical features were consistent with Sorsby's fundus dystrophy. Exon 5 of the gene coding for TIMP-3 was amplified by the polymerase chain reaction, single strand conformation polymorphism analysis undertaken and exon 5 amplicons were directly sequenced.
RESULTS: Onset of symptoms was in the third to fourth decade. Five of six eyes had geographic macular atrophy rather than neovascularisation as a cause for central visual loss. Peripheral retinal pigmentary disturbances were present. Scotopic ERGs were abnormal in all three. Mutation analysis showed a GT transversion in all three resulting in a premature termination codon, E139X, deleting most of the carboxy terminal domain of TIMP-3.
CONCLUSIONS: The patients described had a form of Sorsby's fundus dystrophy which fell at the severe end of the spectrum of this disease. Postulated disease mechanisms include deposition of dimerised TIMP-3 protein
Comparing effects of microplastic exposure, FPOM resource quality, and consumer density on the response of a freshwater particle feeder and associated ecosystem processes
Fine particulate organic matter (FPOM) is an important basal resource in stream ecosystems for deposit- and filter-feeding macroinvertebrates (collectively ‘particle feeders’). Microplastics (MP) share many characteristics with FPOM (e.g. size range, surface area to volume ratios) and are potentially consumed by particle feeders. Accordingly, MP contamination of natural FPOM pools might affect particle feeder growth and survival, particularly when background FPOM resource quality is low, or intraspecific competition is high. We conducted a microcosm experiment to evaluate how a realistic (1400 particles/kg sediment) polyethylene MP (ø = 45–53 µm) concentration interacts with FPOM (ø = 63–250 µm) resource quality (low versus high nutrient content) and consumer density (10 versus 20 individuals per microcosm) to affect growth and survival of larval Chironomus riparius (Diptera: Chironomidae), a model particle feeder. We additionally quantified community respiration, based on three hour measurements of oxygen consumption in the microcosms at the end of the experiment. MP exposure reduced larval body lengths by 26.7%, but only under the low consumer density treatment. MPs reduced community respiration by 26.2%, but only in the absence of chironomids, indicating an impact on microbial respiration. In comparison, low resource quality and high consumer density were associated with 53.5–70.2% reductions in community respiration, chironomid body length and/or body mass. These results suggest that effects of contamination of FPOM with MPs at environmentally realistic concentrations on the life histories of particle feeders such as C. riparius might be limited, especially relative to the effects of resource quality and consumer density. However, the reduction in microbial respiration when MPs were present highlights the need for further research addressing MP impacts on microbes, given their key roles in ecosystem functioning.publishedVersio
Driving Habits, Cognition, and Health-Related Quality of Life in Middle-Aged and Older Adults with HIV
Cognitive impairment is known to increase with aging in people living with HIV (PLWH). Impairment in cognitive domains required for safe driving may put PLWH at risk for poor driving outcomes, decreased mobility, and health-related quality of life (HRQoL). This study described the driving behaviors of middle-aged and older PLWH and examined correlations between driving behaviors and cognitive functioning (Aim 1), and driving behaviors and HRQoL domains (Aim 2). A sample of 260 PLWH ages 40 and older completed a comprehensive assessment including a battery of cognitive tests, an HRQoL measure, and a measure of self-reported driving habits. Associations between driving habits, cognitive function, and HRQoL domains were examined. While 212 (81.54%) participants reported currently driving, only 166 (63.85%) possessed a driver\u27s license. Several significant correlations emerged between driving habits and both cognitive and HRQoL variables, with a general pattern suggesting that current greater driving exposure was associated with better cognitive functioning and HRQoL. Given consistent associations that emerged between the social functioning HRQoL domain and several driving habits, multivariable regression was conducted to examine the unique association between an index of greater driving exposure (i.e., days driven per week) and social functioning, adjusting for potential confounders (race, income, education, depression, and global cognition). Results showed that more days driven per week was a significant, independent correlate of higher social functioning. Understanding the factors underlying driving behaviors in PLWH may contribute to interventions to promote better mobility and improved access to care
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