Membrane transport proteins

Cyclic Adenosine Monophosphate Table Appendix Membrane Transport Proteins Cyclic Guanosine Monophosphate Non-Selective Cation Channels... 

In addition to secretory cells, many non-secretory cells are capable of regulating exocytotic fusion of transport vesicles that are derived from endosomal precursors. For instance, vesicles enriched in plasma membrane transport proteins are incorporated in a regulated manner in order to alter metabolite fluxes. Examples include the glucose transporter GLUT-4 in muscle and fat tissues, a key element in the control of... 

Table appendix Membrane Transport Proteins Aquaporins... 

Membrane Signal Transduction Membrane Transport Protein Menaquinones-n Meniere s Disease Mesangial Cells... 

Resistance to quinolones by efflux has been described in Staph, aureus and Proteus mirabilis. This gene has been designated nor A in Staph, aureus and is homologous to membrane transport proteins coupled to the electromotive force. These proteins have the ability to remove small amounts of quinolone from cells normally and nor A may have arisen as a result of mutations under selective pressure from quinolone use, resulting in a transport protein with increased affinity for these agents. 

Igarashi, P., Cragoe, E.J., Jr. and Aronson, P.S. (1987) Xth ISN Congress Satellite Symposium on Structure, Function and Regulation of Membrane Transport Proteins, Furigen, p. 86. 

W. N. Fischer. B. Andre, D. Rentsch, S. Krolkiewicz, M. Tegeder, K. Breitkreuz, and W. B. Frommer, Amino acid transport in plants. Trends Plant Sci. 3 188 (1998), H. Y. Steiner, W. Song, L. Zhang, F. Naider, J. M. Becker, and G. Stacey, An Arahidopsis peptide transporter is a member of a novel family of membrane transport proteins. Plant Cell 6 189 (1994). 

P-glycoprotein, a plasma membrane transport protein, is present in the gut, brain, liver, and kidneys 42 This protein provides a biologic barrier by eliminating toxic substances and xenobiotics that may accumulate in these organs. P-glycoprotein plays an important role in the absorption and distribution of many medications. Medications that are CYP3A4 substrates, inhibitors, or inducers are also often affected by P-glycoprotein therefore, the potential for even more DDIs exists in transplant recipients.42... 

Hediger, M.A., Romero, M.F., Peng, J.B., Rolfs, A., Takanaga, H. and Bruford, E.A. (2004) The ABCs of solute carriers physiological, pathological and therapeutic implications of human membrane transport proteins. Pflugers Archiv, 447, 465-468. 

Unconjugated bilirubin is taken into the hepatocytes by binding to membrane transport proteins and transported through the liver cells to the SER by proteins called ligandins. The SER is the location of a specific bilirubin-UDP-glucuronosyl transferase... 

Yao SYM, Cass CE, Young JD. 2000. The Xenopus oocyte e3q>ression system for the cDNA cloning and characterization of plasma membrane transport proteins. In Membrane transport A Practical Approach. Baldwin SA, editor. Oxford University Press, Oxford, pp. 47-78. 

MPTP) and sodium benzoate induce a strong downregulation in the expression of tyrosine hydroxylase mRNA and in the tyrosine hydroxylase-positive cells in the ventral diencephalon. These chemicals also decreased the expression of the dopamine transporter (DAT), a membrane transport protein involved in dopamine reuptake, that is, a specific marker of dopaminergic neurons [9]. 

Drug resistance in vitro and probably in vivo results both from inhibition of influx of the vinca alkaloids and, perhaps more frequently, from promotion of their efflux out of cells (34,35). Until relatively recently, the former mechanism was thought to predominate, and, indeed, certain acquired drug-resistant states are clearly associated with the loss of membrane proteins which can be shown to bind and transport agents into cells (34). However, other resistant states have been shown to be associated with the acquisition of membrane transport proteins which remove toxins (and, therefore, chemotherapeutic agents) both from normal and malignant cells. 

Almost all diuretics exert their action at the luminal surface of the renal tubule cells. Their mechanism of action includes interaction with specific membrane transport proteins like thiazides, furosemide etc., osmotic effects which prevent the water permeable segments of the nephron from absorbing water like mannitol, and specific interaction with enzyme like carbonic anhydrase inhibitors i.e. acetazolamide, and hormone receptors in renal epithelial cells like spironolactone. 

This chapter is divided into three sections. The first section covers renal tubule transport mechanisms. The nephron is divided structurally and functionally into several segments (Figure 15-1, Table 15-1). Many diuretics exert their effects on specific membrane transport proteins in renal tubular epithelial cells. Other diuretics exert osmotic effects that prevent water reabsorption (mannitol), inhibit enzymes (acetazolamide), or interfere with hormone receptors in renal epithelial cells (aldosterone receptor blockers). The physiology of each segment is closely linked to the basic pharmacology of the drugs acting there, which is discussed in the second section. Finally, the clinical applications of diuretics are discussed in the third section. 

Membrane transporter proteins (MDR or ABC transporter proteins) such as p-glycoprotein are crucially important in the process of excretion and also in absorption and distribution and elimination of chemicals from cells. These transport organic anions or cations and neutral compounds across membranes, pump unwanted chemicals out of cells such as in gut, placenta, and brain, transport chemicals into bile from liver cells, and facilitate excretion from the kidney. 

---