Clathrin-coated vesicles transport selected integral membrane proteins from the cell surface and the trans-Golgi network to the endosomal system. Before fusing with their target the vesicles must be stripped of their coats. This process is effected by the chaperone protein hsp70c together with a 100K cofactor which we here identify as the coat protein auxilin. Auxilin binds with high affinity to assembled clathrin lattices and, in the presence of ATP, recruits hsp70c. Dissociation of the lattice does not depend as previously supposed on clathrin light chains or on the amino-terminal domain of the heavy chain. The presence of a J-domain at its carboxy terminus now defines auxilin as a member of the DnaJ protein family. In conjunction with hsp70, DnaJ proteins catalyse protein folding, protein transport across membranes and the selective disruption of protein-protein interactions. We show that deletion of the J-domain of auxilin results in the loss of cofactor activity.
T he ongoing obesity epidemic and its impending cardiovascular consequences represent a serious public health problem with worrisome implications for medical treatment. The urgency of providing new research directions recently led the National Heart, Lung, and Blood Institute (NHLBI) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) to convene a Working Group on the Pathophysiology of Obesity-Associated Cardiovascular Disease. Gathered at this meeting were researchers with substantial experience and expertise in either obesity-related sciences, including epidemiology, endocrinology, and metabolism, or cardiovascular sciences, including cardiology, neurobiology, hematology, renal function, and pediatrics. This report is the culmination of the blending of ideas during the 2-day meeting. The resulting research recommendations include the development of new models and synergistic approaches to basic studies of obesity-associated cardiovascular diseases. BackgroundThe adult US population, whose combined prevalence of overweight and obesity now exceeds 60%, 1 is experiencing an unprecedented exposure to obesity-related cardiovascular risk factors and is expected to suffer the adverse clinical consequences in years to come. Also alarming are the ever-rising rates of overweight and obese children and adolescents, which have tripled over the last 30 years. 2 Increased rates of co-morbidities such as dyslipidemia, hypertension, type 2 diabetes, and hepatic damage in overweight adolescents indicate that the young are not protected from the metabolic perturbations that accompany excess adipose tissue stores. [3][4][5] We do not know what the consequences might be for the developing cardiovascular system if obesity is present during late stages of growth and maturation.Overweight or obese individuals experience greatly elevated morbidity and mortality from nearly all of the common cardiovascular diseases (stroke, coronary heart disease, congestive heart failure, cardiomyopathy, and possibly arrhythmia/sudden death). 6,7 Because primary treatment and prevention of obesity often fail or are only partially successful, it is anticipated that the future will bring ever-increasing demands to treat the cardiovascular conditions attributable to obesity. Thus, to develop rational therapeutic approaches, we need to understand the basic biology of obesity-related cardiovascular diseases and disorders. Discussion HighlightsThe Working Group's multi-disciplinary panel of clinical and basic scientists was charged with evaluating the current state of the science on basic mechanisms of obesity-associated cardiovascular disease and identifying research opportunities with a focus on potential therapeutic applications. The group was encouraged to translate problems identified through population and clinical research into clear priorities for mechanistic research. Mechanistic Studies in Animals and Humans Adipose Tissue as a Metabolically Active Endocrine OrganThe predominant role of adipose tissue is the storage ...
We have studied the direct interaction of the constitutive isoform of Hsp70 (Hsc70) with the DnaJ homolog, auxilin, a cofactor that binds to clathrin-coated vesicles and is required for their uncoating by Hsc70. Auxilin caused a 5-fold increase in Hsc70 ATPase activity and a corresponding increase in steady-state levels of bound ADP; the dissociation constant for this effect was 0.6 M. Auxilin also induced polymerization of Hsc70 and bound to the resulting polymer at a 1:1 molar ratio; here too the dissociation constant was 0.6 M. Both this binding and polymerization required ATP; the Hsc70 depolymerized with a 4-min half-life when ATP was completely hydrolyzed to ADP. Although auxilin induces polymerization stoichiometrically and other DnaJ homologs induce polymerization catalytically, these data show that auxilin is similar to other DnaJ homologs in its ability to activate the Hsc70 ATPase activity, to polymerize Hsc70, and in the nucleotide dependence of this polymerization. Furthermore, the 70-amino acid J-domain of auxilin polymerized Hsc70 with the same nucleotide dependence as intact auxilin. Therefore, although only auxilin and not other DnaJ homologs support uncoating, our data suggest that various DnaJ homologs share a common mechanism of interaction with Hsc70, perhaps because their J-domains interact similarly with Hsc70.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.