Up- and down-regulation of insulin receptors. Kinetic models

Identification of dominant signaling pathways from proteomics expression data

The availability of the results of high-throughput analyses coming from 'omic' technologies has been one of the major driving forces of pathway biology. Analytical pathway biology strives to design a 'pathway search engine', where the input is the 'omic' data and the output is the list of activated or dominant pathways in a given sample. Here we describe the first attempt to design and validate such a pathway search engine using as input expression proteomics data. The engine represents a specific workflow in computational tools developed originally for mRNA analysis (BMC Bioinformatics 2006, 7 (Suppl 2), S13). Using our own datasets as well as data from recent proteomics literature we demonstrate that different dominant pathways (EGF, TGF(beta), stress, and Fas pathways) can be correctly identified even from limited datasets. Pathway search engines can find application in a variety of proteomics-related fields, from fundamental molecular biology to search for novel types of disease biomarkers.

Membrane receptors in the gastrointestinal tract

This review focusses on the roles that membrane receptors and their transducers play in the physiology and pathology of the gastrointestinal tract. The multifactorial regulation of [correction] mucosal growth and function is discussed in relation to the heterogeneity of exocrine and endocrine populations that originate from progenitor cells in stomach and intestine.

Low density lipoprotein receptor regulation. Kinetic models

The macromolecular species distribution in a receptor-mediated endocytotic pathway was computer simulated based on kinetic data reported in the literature. In the proposed model, the rapidity with which the recycled receptor is shuttled to the cell surface is indicated by the magnitude of k-3, the shuttling constant. The magnitude of k-3 will vary with the experimental conditions, but when this value is large, the internalized receptor is shuttled back to the cell surface with a traverse time of 14 min. Under steady-state conditions, after the cells have been incubated in the presence of LDL for 5 h (M.S. Brown and J.L. Goldstein, Cell 9 (1976) 663), the time required for a receptor to traverse the entire endocytotic pathway is 52 min. Our simulation suggests that normal LDL binding in such a short-term experiment may be independent of receptor synthesis. Thus, the degradation of LDL and resultant build-up of cholesterol would have no apparent inhibitory effect on the down-regulation of receptor synthesis.