Chapter 6 Protein Sorting in the Secretory Pathway

Use of Targeting Agents to Increase Uptake and Localization of Drugs to the Intestinal Epithelium

Despite early successes in oral drug delivery of small molecules such as antibiotics, cephalosporins and vitamins, little success has been achieved with more recent pharmaceuticals such as peptides and proteins. This lack of success is primarily due to the impenetrable nature of the gastro-intestinal epithelial cell layers. Despite this, many bacteria, viruses and toxins are readily taken up from the intestine and thereby gain entry into the circulation. This review focuses on the use of various surface molecules from these organisms as well as toxin binding subunits as carriers for oral delivery of other molecules. It also describes the subversion of the natural uptake mechanisms for various vitamins and iron to allow for oral delivery of pharmaceuticals. These mechanisms provide exciting solutions to overcome the problems in oral delivery of peptides and proteins, which has been the nemesis of pharmaceutical scientists for many decades.

Molecular sorting in the secretory pathway

Proteins can be secreted from animal cells by either a constitutive or a regulated pathway; those destined for regulated secretion are actively sorted into dense-core secretory granules. Although sorting is generally assumed to be accomplished by specific carriers, the nature of these carriers remains elusive. In this study, peptide hormones were used as affinity ligands to purify a set of 25-kilodalton proteins from canine pancreatic tissue. Their ligand specificities and patterns of expression have the characteristics of sorting carriers.

Molecular biology and the diagnosis, epidemiology and pathogenesis of infectious diseases

In this short review, the impact of molecular biology on microbiology in general is described. Specifically, molecular biology is increasingly enlarging the available choice of methods for the diagnosis of microbial disease. In situ hybridization seems to be a particularly promising procedure. In epidemiology, an interesting facet is the high mutation rate of RNA viruses. In pathogenesis, molecular biology will help to elucidate pathways of infection and the targeting of pathogenic macromolecules within the cell and within an organism.