Biomedical subjects

Catherine L Higgins

Publications and source records attributed to Catherine L Higgins.

6 recordsLinked to original sources

PubMed2006

Quantitation and localization of matrix metalloproteinases and their inhibitors in human carotid endarterectomy tissues.

BACKGROUND: Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) play a central role in arterial wall remodeling, affecting stability of fibrous caps covering atherosclerotic plaques. The objective of this study was to determine the spatial distribution of TIMP mass and MMP mass and activity of carotid endarterectomy (CEA) tissues and relate it to the distribution of atherosclerotic lesions. METHODS AND RESULTS: Fresh CEA tissues were imaged by multicontrast MRI to generate 3D reconstructions. Tissue segments were cut transversely from the common, bifurcation, internal, and external regions. Segments were subjected to total protein extractions and analyzed by ELISA for MMP-2 and -9 and TIMP-1 and -2 mass and by zymography for gelatinase activity. Segments at or near the bifurcation with highly calcified lesions contained higher MMP levels and activity than segments distant from the bifurcation; highly fibrotic or necrotic plaque contained lower MMP levels and activity and higher TIMP levels. Fatty streak, fibroatheroma with hemorrhage and calcification, and fully occluded lesions were enriched in MMP-2, MMP-9, and TIMP-1 and TIMP-2, respectively. CONCLUSIONS: The spatial distribution of MMPs and TIMPs in carotid atherosclerotic lesions is highly heterogeneous, reflecting lesion location, size, and composition. This study provides the first semi-quantitative maps of differential distribution of MMPs and TIMPs over atherosclerotic plaques.

Carotid Arteries↗

PubMed2005

Quantification of calcification in atherosclerotic lesions.

Calcification can be deposited throughout the vasculature in several forms of calcium phosphate, including calcium hydroxyapatite (CHA). Calcium accumulation in arteries by mineralization and calcium loss from bone by osteoporosis often coexist, and vascular calcification may share common mechanisms with bone remodeling. Deposition of calcification in valves and arteries diminishes the valvular or arterial wall elasticity, a major cause of aneurysm and stenosis. Obstruction of arteries by calcification and other components can lead to heart attack and stroke. Mineralization in the femoral arteries can cause intermittent claudication in the legs, causing decreased mobility. Accurate measurement of calcification is essential for identifying other factors associated with this process and ultimately for elucidating the mechanism(s) of calcification. A wide range of methods for visualizing and measuring calcification for diagnosis and treatment in vivo and for studying the calcification process ex vivo are available. This review provides a critical comparison of older established methods and newer evolving technologies for quantifying calcification.

Animals↗

PubMed2005

How do cofactors modulate protein folding?

Cofactors are essential components of many proteins for biological activity. Characterization of several cofactor-binding proteins has shown that cofactors often have the ability to interact specifically with the unfolded polypeptides. This suggests that cofactor-coordination prior to polypeptide folding may be a relevant path in vivo. By binding before folding, the cofactor may affect both the mechanism and speed of folding. Here, we discuss three different cofactors that modulate protein-folding processes in vitro.

Animals↗

PubMed2004

Formation of linear three-iron clusters in Aquifex aeolicus two-iron ferredoxins: effect of protein-unfolding speed.

The presence of a linear [3Fe-4S] cluster in a protein was first observed in beef-heart aconitase. Here, we report the formation of linear [3Fe-4S] clusters upon guanidine hydrochloride (GuHCl)-induced unfolding of Aquifex aeolicus [2Fe-2S] ferredoxins (Fd) (AaeFd1, AaeFd4, and AaeFd5) at alkaline conditions (pH 10, 20 degrees C). We find the mechanism of linear [3Fe-4S] cluster formation to depend critically on the speed of polypeptide unfolding. In similarity to seven-iron Fds, polypeptide unfolding determines the rate by which linear [3Fe-4S] clusters form in AaeFd4 and AaeFd5. In contrast, in a disulfide-lacking variant of AaeFd1, which unfolds faster than AaeFd4 and AaeFd5, the polypeptides unfold first and the majority of clusters decompose. Next, unfolded polypeptides retaining intact clusters scavenge iron and sulfur to form linear [3Fe-4S] clusters in a bimolecular reaction. Wild-type AaeFd1 unfolds slower than the speed of linear-cluster decomposition, and the linear species is never populated. Linear [3Fe-4S] clusters may be intermediates during folding of iron-sulfur proteins.

Bacterial Proteins↗

PubMed2003

High thermal and chemical stability of Thermus thermophilus seven-iron ferredoxin. Linear clusters form at high pH on polypeptide unfolding.

To probe the stability of the seven-iron ferredoxin from Thermus thermophilus (FdTt), we investigated its chemical and thermal denaturation processes in solution. As predicted from the crystal structure, FdTt is extremely resistant to perturbation. The guanidine hydrochloride-induced unfolding transition shows a midpoint at 6.5 m (pH 7, 20 degrees C), and the thermal midpoint is above boiling, at 114 degrees C. The stability of FdTt is much lower at acidic pH, suggesting that electrostatic interactions are important for the high stability at higher pH. On FdTt unfolding at alkaline pH, new absorption bands at 520 nm and 610 nm appear transiently, resulting from rearrangement of the cubic clusters into linear three-iron species. A range of iron-sulfur proteins has been found to accommodate these novel clusters in vitro, although no biological function has yet been assigned.

Bacterial Proteins↗

PubMed2002

Exceptional stability of a [2Fe-2S] ferredoxin from hyperthermophilic bacterium Aquifex aeolicus.

Aquifex aeolicus is the only hyperthermophile that is known to contain a plant- and mammalian-type [2Fe-2S] ferredoxin (Aae Fd1). This unique protein contains two cysteines, in addition to the four that act as ligands of the [2Fe-2S] cluster, which form a disulfide bridge. We have investigated the stability of Aae Fd1 with (wild-type) and without (C87A variant) the disulfide bond, with respect to pH, thermal and chemical perturbation, and compared the results to those for the mesophilic [2Fe-2S] ferredoxin from spinach. Unfolding reactions of all three proteins are irreversible due to cluster decomposition in the unfolded state. Wild-type and C87A Aae Fd1 proteins are extremely stable: unfolding at 20 degrees C requires high concentrations of the chemical denaturant and long incubation times. Moreover, their thermal-unfolding midpoints are 40-50 degrees higher than that for spinach ferredoxin (pH 7). The stability of the Aae Fd1 protein is significantly lower at pH 2.5 than pH 7 and 10, suggesting that ionic interactions play a role in structural integrity. Interestingly, the iron-sulfur cluster in C87A Aae Fd1 rearranges into a transient species with absorption bands at 520 and 610 nm, presumably a linear three-iron cluster, in the high-pH unfolded state.

Bacteria↗