Processing of the insulin-like growth factor-II–mannose 6-phosphate receptor in isolated liver subcellular fractions

2001 ◽  
Vol 79 (4) ◽  
pp. 469-477
Author(s):  
Khadija Tahiri ◽  
Laurence Cam ◽  
Bernard Desbuquois ◽  
Geneviève Chauvet
Keyword(s):  
Plasma Membrane ◽  
Growth Factor ◽  
Polyacrylamide Gel Electrophoresis ◽  
Subcellular Fractions ◽  
Soluble Form ◽  
Dependent Manner ◽  
Insulin Like Growth Factor ◽  
Factor Ii ◽  
Mannose 6 Phosphate ◽  
Isolated Liver

A truncated, soluble form of the insulin-like growth factor-II–mannose 6-phosphate (IGF-II–M6P) receptor has been identified in serum and shown to be released from cultured tissues and cells, liver being the main contributor to serum receptor in adult rats. In the present study, the processing of the IGF-II–M6P receptor has been characterized in isolated liver subcellular fractions using ligand binding, affinity crosslinking, and Western immunoblotting techniques. The receptor in plasma membrane fractions differed from that in Golgi-endosomal fractions by: (i) a lower molecular size upon reducing polyacrylamide gel electrophoresis (245 vs. 255 kDa); (ii) a less tight membrane association as judged upon extractibility by NaCl; and (iii) the inability to recognize antibody anti-22C, directed against the cytoplasmic domain of the receptor. Incubation of cell fractions at 30°C led to a pH- and time-dependent release of the receptor into the medium. The pH optimum for release was 5.5 in the Golgi-endosomal fraction and 7.5 in plasma membrane fractions; at this pH, approximately 2% and 20%–30% of total receptors were released per hour, respectively. Receptor release was inhibited in a dose-dependent manner by aprotinin, benzamidine, and leupeptin in the Golgi-endosomal fraction, and by 1,10 phenanthroline in plasma membrane fractions, although high concentrations were required for inhibition. The receptor released from Golgi-endosomes showed a 5–10 kDa reduction in size and a loss of ability to recognize antibody anti-22C, but that released from plasma membranes showed little or no changes in size. We conclude that soluble, carboxy-terminally truncated forms of the IGF-II–M6P receptor are generated from the intact receptor in isolated Golgi-endosomal and plasma membrane fractions. However, receptor processing in these fractions exhibits different properties, suggesting the involvement of different proteases.Key words: insulin-like growth factor-II–mannose 6-phosphate (IGF-II–M6P) receptor, liver, plasma membrane, Golgi apparatus, endosomes.

scholarly journals The cytoplasmic tail of the mannose 6-phosphate/insulin-like growth factor-II receptor has two signals for lysosomal enzyme sorting in the Golgi.

1992 ◽  
Vol 119 (2) ◽  
pp. 249-257 ◽  
Author(s):  
K F Johnson ◽  
S Kornfeld
Keyword(s):  
Plasma Membrane ◽  
Growth Factor ◽  
Cytoplasmic Tail ◽  
Adaptor Proteins ◽  
Carboxyl Terminus ◽  
Insulin Like Growth Factor ◽  
Factor Ii ◽  
Carboxyl Terminal ◽  
Mannose 6 Phosphate ◽  
Mutant Receptors

The mannose 6-phosphate/insulin-like growth factor-II (Man-6-P/IGF-II) receptor is known to cycle between the Golgi, endosomes, and the plasma membrane. In the Golgi the receptor binds newly synthesized lysosomal enzymes and transports them directly to an endosomal (prelysosomal) compartment without traversing the plasma membrane. Deletion of the carboxyl-terminal Leu-Leu-His-Val residues of the 163 amino acid cytoplasmic tail of the bovine Man-6-P/IGF-II receptor partially impaired this function, resulting in the diversion of a portion of the receptor-ligand complexes to the cell surface, where they were endocytosed. The same phenotype was observed when 134 residues of the cytoplasmic tail were deleted from the carboxyl terminus. Disruption of the Tyr24-Lys-Tyr-Ser-Lys-Val29 plasma membrane internalization signal alone had little effect on Golgi sorting, but when combined with either deletion resulted in a complete loss of this function. The mutant receptors retained the ability to recycle to the Golgi and bind cathepsin D. These results indicate that the cytoplasmic tail of the Man-6-P/IGF-II receptor contains two signals that contribute to Golgi sorting, presumably by interacting with the Golgi clathrin-coated pit adaptor proteins. The Leu-Leu-containing sequence represents a novel motif for mediating interaction with Golgi adaptor proteins.

Mannose 6-phosphate Receptor (MPR 300) Proteins from Goat and Chicken Bind Human IGF-II

2006 ◽  
Vol 26 (2) ◽  
pp. 101-112 ◽  
Author(s):  
Suresh Koduru ◽  
Sivaramakrishna Yadavalli ◽  
Siva Kumar Nadimpalli
Keyword(s):  
Plasma Membrane ◽  
Growth Factor ◽  
Lysosomal Enzymes ◽  
Growth Factor Receptor ◽  
Cell Receptor ◽  
Insulin Like Growth Factor ◽  
Fish Embryo ◽  
Multifunctional Protein ◽  
Factor Ii ◽  
Mannose 6 Phosphate

Mannose 6-phosphate receptor proteins (MPR 300 and 46) in mammals have been shown to mediate transport of lysosomal enzymes to lysosomes intracellularly. Both receptors are also expressed on the plasma membrane. Only MPR 300 protein on the plasma membrane has been shown to be a multifunctional protein which in addition to binding mannose 6-phosphate containing proteins also binds human insulin-like growth factor-II (IGF-II) causing its internalization [Hille-Rehfeld, A. (1995) Mannose 6-phosphate receptors in sorting and transport of lysosomal enzymes. Biochim. Biophys. Acta. 1241: 177–194]. This property has been shown to be exhibited by other mammalian receptors but not by the chicken and frog receptors. In a recent study however it was shown that the fish embryo MPR 300 binds human IGF-II. [Mendez, E., Planas, J.V., Castillo, J., Navarro, I. and Gutierrez, J. (2001) Identification of a type II insulin-like growth factor receptor in fish embryos. Endocrinology, 142: 1090–1097]. In the present study, we demonstrate that the purified goat and chicken liver receptors bind human IGF-II by employing cross-linking experiments (purified receptors and radiolabeled IGF-II) and by ligand blotting (using purified receptors and biotinylated IGF-II). Further CEF cells (chicken embryonic fibroblasts) that are known to contain the putative MPR 300 protein were employed to demonstrate that the CEF cell receptor binds human IGF-II.

scholarly journals Regulation of Soluble Insulin-Like Growth Factor II/Mannose 6-Phosphate Receptor in Human Serum: Measurement by Enzyme-Linked Immunosorbent Assay1

1999 ◽  
Vol 84 (2) ◽  
pp. 611-617 ◽  
Author(s):  
Michael Costello ◽  
Robert C. Baxter ◽  
Carolyn D. Scott
Keyword(s):  
Diabetes Mellitus ◽  
Growth Factor ◽  
Soluble Form ◽  
Dependent Diabetes Mellitus ◽  
Enzyme Linked Immunosorbent Assay ◽  
Hepatoma Cell Line ◽  
Insulin Like Growth Factor ◽  
Soluble Receptor ◽  
Factor Ii ◽  
Mannose 6 Phosphate

The soluble form of the insulin-like growth factor II/mannose 6-phosphate (IGF-II/M6-P) receptor has been detected in serum from a variety of mammalian species. We report the development of a highly sensitive quantitative human IGF-II/M6-P receptor immunoassay. Antibodies raised to receptor purified from a human hepatoma cell line by phosphomannan affinity chromatography were used to develop a specific enzyme-linked immunosorbent assay. In this assay, the serum level of soluble receptor for healthy adult subjects was 0.70 ± 0.23 mg/L. We have shown that soluble receptor is developmentally regulated, with levels in infant (1.12 ± 0.28 mg/L) and prepubertal (1.18 ± 0.6 mg/L) subjects dropping by 40% during adolescence (0.73 ± 0.61 mg/L) and remaining constant throughout adulthood. Further, the receptor is gestationally regulated, with a highly significant association between gestational age and maternal serum receptor levels (r = 0.947; P < 0.0001). Noninsulin-dependent diabetes mellitus (0.98 ± 0.25 mg/L) and insulin-dependent diabetes mellitus (0.98 ± 0.25 mg/L) mildly elevated soluble receptor levels, whereas end-stage renal failure (0.75 ± 0.23 mg/L) and acromegaly (0.79 ± 0.25 mg/L) did not affect receptor levels. Additionally, we have shown that soluble receptor is present in amniotic fluid, but at a 100-fold lower concentration than serum levels. The ability to quantitate soluble IGF-II/M6-P receptor levels in serum and other fluids provides a valuable tool that will help to further elucidate the role of the receptor in human physiology and disease states.

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