Glycoprotein Function

WANG E, BARECKi-ROACH M, JOHNSON w (2002) Elevation of P-glycoprotein function by a catechin in green tea. Biochem Biophys Res Commun. 297 412. 

Current understanding of parasitism by T. spiralis is compartmentalized, and so glycoprotein function has been considered in the context of one compartment or another. However, LI larvae of T. spiralis have evolved under selective pressure to parasitize both intestine and muscle. Biological economy may require a duality of function in larval glycoproteins such that they are able to perform distinct roles in each of the two niches. Dualism is common in proteins, and elucidation of such properties in parasitic nematode products would provide unique insights into the basis of host adaptation. 

D. D. Breimer. Specificity of doxorubicin versus rhodamine-123 in assessing P- glycoprotein functionality in the LLC-PK1, LLC-PK1 MDR1 and Caco-2 cell lines, Ear. J. Pharm. Sci. 2000, 11, 207-214... 

Terao, T., Hisanaga, E., Sai, Y., Tamai, I., Tsuji, A., Active secretion of drugs from the small intestinal epithelium in rats by P-glycoprotein functioning as an absorption barrier,... 

Fig. 8.4 P-glycoprotein function in CD56+ natural killer cells of healthy volunteers according to MDR7 genotype at position 3435. Panel A Rhodamine fluorescence of CD56+ natural killer cells in two healthy individuals with different MDR1 genotypes in exon 26 (position 3435) after an efflux period of lOmin (gray line) compared to control cells (i.e., fluorescence of cells from the same individuals incubated for lOmin...

Takano, A., Kusuhara, H., Suhara, T., Ieiri, I Morimoto,T., Lee, Y.J., Maeda, J., Ikoma, Y., Ito, H., Suzuki, K. and Sugiyama, Y. (2006) Evaluation of in vivo P-glycoprotein function at the blood-brain barrier among MDR1 gene polymorphisms by using HC-verapamil. Journal of Nuclear Medicine, 47, 1427-1433. 

The permeability of the drug substance can be determined by different approaches such as pharmacokinetic studies in humans (fraction absorbed or mass balance studies) or intestinal permeability studies (in vivo intestinal perfusion studies in humans or suitable animal models or in vitro permeation studies using excised intestinal tissue or epithelial cell culture monolayers like CaCo-2 cell line). In order to avoid misclassification of a drug subject to efflux transporters such as P-glycoprotein, functional expression of such proteins should be investigated. Low- and high-permeability model... 

Iida A, Tomita M, Hayashi M (2005) Regional difference in P-glycoprotein function in rat intestine. Drug Metab Pharmacokinet 20 100-106... 

Profit L, Eagling VA, Back DJ (1999) Modulation of P-glycoprotein function in human lymphocytes and Caco-2 cell monolayers by HIV-1 protease inhibitors. AIDS 13 1623-1627. 

Shen Q, Lin Y, Handa T, Doi M, Sugie M, Wakayama K, Okada N, Fujita T, Yamamoto A (2006) Modulation of intestinal P-glycoprotein function by polyethylene glycols and their derivatives by in vitro transport and in situ absorption studies. Int J Pharm 313 49-56. 

One possibility to enhance, in a controlled manner, entry of drugs into the CNS would be to alter P-glycoprotein function at the blood-brain barrier. Such an enhancement could result from (1) direct modification of export pump function by inhibitors and intracellular signals or (2) bypassing the export pump by delivery systems not being recognized as substrates (e.g., nanoparticles or vector-coupled liposomes, which are taken up by endocytotic mechanisms) [58-65],... 

Kopnin BP, Stromskaya TP, Kondratov RV, Ossovskaya S, Pugacheva EN, Rybalkina EY, Khokhlova OA, Chumakov PM (1995) Influence of exogenous ras and p53 on P-glycoprotein function in immortalized rodent fibroblasts. Oncol Res 7 299-306... 

Nabekura T, Kamiyama S, Kitagawa S. 2005. Effects of dietary chemopreventive phytochemicals on P-glycoprotein function. Biochem Biophys Res Commtm 327 866-870. 

Walker, J., C. Martin, and R. Callaghan. 2004. Inhibition of P-glycoprotein function by XR9576 in a solid tumour model can restore anticancer drug efficacy. Eur J Cancer 40 594. 

Upreti, R. K., Kumar, M., and Shankar, V. (2003) Bacterial glycoproteins functions, biosynthesis and applications. Proteomics 3,363-379. 

Lee YJ, Maeda J, Kusuhara H, et al. In vivo evaluation of P-glycoprotein function at the blood-brain barrier in nonhuman primates using [1 lC]verapamil. J Pharmacol Exp Ther 2006 316 647-653. 

Shono Y., Nishihara H., Matsuda Y., Furukawa S., Okada N., Fujita T., Yamamoto A. (2004) Modulation of intestinal P- glycoprotein function by cremophor EL and other surfactants by an in vitro diffusion chamber method using the isolated rat intestinal membranes. J Pharm Sci, 93 877-885. 

As mentioned in Section 17.2.1, HA is a spike glycoprotein anchored to the virus lipid membrane [50], This glycoprotein functions as a receptor-binding protein and is responsible for the first step of viral infection when it binds to sialic acid residues of receptor glycoproteins on host cells [18]. When the virus is endocytosed into the cell, the low pH (5-6) changes the structure of HA, and this new fusion-active state triggers the fusion of the viral membrane and the endosome membrane, ultimately allowing entry of the viral nucleocapsid into the cytosol of the host cell [18]. 

Schalich, J., Allison, S. L., Stiasny, K., Mandl, C. W., Kunz, C., and Heinz, F. X. (1996). Recombinant subviral particles from tick-borne encephalitis virus are fusogenic and provide a model system for studying flavivirus envelope glycoprotein functions. 

The structure of P-glycoprotein has not been determined. However, X-ray crystallographic structures have been determined for bacterial members of the ABC transporter family the MsbA lipid A "flippases" from E. coli (72) and Vibrio cholera (73) and the cobal-amin uptake transporter BtuCD protein of E. coli (74). These structures are consistent with the overall picture of P-glycoprotein function described here. 

P-Glycoprotein functions in the gut primarily to affect the rate rather than the extent of drug absorption (68) (see Chapter 4, Figure 4.2). However, P-gp increases substrate exposure to luminal CYP3A4 metabolism during the process of drug efflux. Consequently, coadministration of a CYP3A4-P-gp... 

ORIGIN Anterior pituitary gland (basophil cells) STRUCTURE Both are glycoproteins FUNCTION In males, LH stimulates testosterone synthesis in the testes, whereas FSH stimulates spermato-... 

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