The work proposed aims to determine whether during maturation, all immature mammalian red cells lose selected membrane components, and in particular, the transferrin receptor by the extrusion of membrane limited vesicles. The objective is to determine whether (and how) the protein and enzyme activities of these vesicles varies between species, and how (or if) this variation reflects the components disappearing from the red cell during maturation. The work involves the use of various species made anemic by phlebotomy or phenyl hydrazine treatment, separation of vesicles from the plasma or culture medium. The analysis of the protein content is by SDS-PAGE as well as with specific antibodies, such as those for the transferrin receptor and the clathrin uncoating ATPase and assays for specific enzymes and functions, such as nucleoside transport. The stage of the life cycle of the red cell at which vesicle formation starts is known. To address this question, immature, nucleated red blood cells from spleens of anemic mice will be isolated and cultured to determine whether vesicle formation is a postenucleation event. To address the question whether a single vesicle contains all the lost activities or ether these are segregated amongst different vesicles, the isolated vesicles from maturing sheep reticulocytes will be separated by isoelectric focusing or chromato-focusing to see if the specific functions can be segregated. Electron microscopic studies using gold labelled antibodies to detect specific functions will be used to confirm whether a single vesicle is a repository for several functions. Red cells lose many plasma membrane functions during maturation. It is not known whether all these functions are lost with a common time frame. It is proposed to address the time course for the loss of several selected functions and whether physiological significance can be attributed to the putative differences in rate of loss. The ultimate objective is to determine what signals are used to eliminate obsolete, but still functional membrane proteins, during maturation of the red cell. Circulating transferrin receptors have been detected in man during elevated reticulocyte formation and in some malignancies. Knowledge of the composition of the released vesicles and the type of proteins lost may provide additional approaches to diagnosis of malignancy and aberration in red cell production.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK040299-02
Application #
3240471
Study Section
Hematology Subcommittee 2 (HEM)
Project Start
1988-09-26
Project End
1991-08-31
Budget Start
1989-09-01
Budget End
1990-08-31
Support Year
2
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Mcgill University
Department
Type
DUNS #
City
Montreal
State
PQ
Country
Canada
Zip Code
H3 2T5
Weeks 2nd, James L; Zoraghi, Roya; Francis, Sharron H et al. (2007) N-Terminal domain of phosphodiesterase-11A4 (PDE11A4) decreases affinity of the catalytic site for substrates and tadalafil, and is involved in oligomerization. Biochemistry 46:10353-64
Zoraghi, Roya; Francis, Sharron H; Corbin, Jackie D (2007) Critical amino acids in phosphodiesterase-5 catalytic site that provide for high-affinity interaction with cyclic guanosine monophosphate and inhibitors. Biochemistry 46:13554-63
Blount, Mitsi A; Zoraghi, Roya; Bessay, Emmanuel P et al. (2007) Conversion of phosphodiesterase-5 (PDE5) catalytic site to higher affinity by PDE5 inhibitors. J Pharmacol Exp Ther 323:730-7
Zoraghi, Roya; Corbin, Jackie D; Francis, Sharron H (2006) Phosphodiesterase-5 Gln817 is critical for cGMP, vardenafil, or sildenafil affinity: its orientation impacts cGMP but not cAMP affinity. J Biol Chem 281:5553-8
Blount, Mitsi A; Zoraghi, Roya; Ke, Hengming et al. (2006) A 46-amino acid segment in phosphodiesterase-5 GAF-B domain provides for high vardenafil potency over sildenafil and tadalafil and is involved in phosphodiesterase-5 dimerization. Mol Pharmacol 70:1822-31
Corbin, J; Francis, S; Zoraghi, R (2006) Tyrosine-612 in PDE5 contributes to higher affinity for vardenafil over sildenafil. Int J Impot Res 18:251-7
Zoraghi, Roya; Bessay, Emmanuel P; Corbin, Jackie D et al. (2005) Structural and functional features in human PDE5A1 regulatory domain that provide for allosteric cGMP binding, dimerization, and regulation. J Biol Chem 280:12051-63
Zoraghi, Roya; Corbin, Jackie D; Francis, Sharron H (2004) Properties and functions of GAF domains in cyclic nucleotide phosphodiesterases and other proteins. Mol Pharmacol 65:267-78
Johnstone, R M; Mathew, A; Setchenska, M S et al. (1998) Loss of glucose transport in developing avian red cells. Eur J Cell Biol 75:66-77
Johnstone, R M (1996) Cleavage of the transferrin receptor by human granulocytes: differential proteolysis of the exosome-bound TFR. J Cell Physiol 168:333-45

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