A highly phosphorylated subpopulation of insulin-like growth factor II/mannose 6-phosphate receptors is concentrated in a clathrin-enriched plasma membrane fraction.

A truncated, soluble form of the insulin-like growth factor-IImannose 6-phosphate (IGF-IIM6P) 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-IIM6P 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 510 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-IIM6P 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-IImannose 6-phosphate (IGF-IIM6P) receptor, liver, plasma membrane, Golgi apparatus, endosomes.

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

The Journal of Cell Biology ◽

10.1083/jcb.119.2.249 ◽

1992 ◽

Vol 119 (2) ◽

pp. 249-257 ◽

Cited By ~ 131

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.

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Glucose Increases Both the Plasma Membrane Number and Phosphorylation of Insulin-like Growth Factor II/Mannose 6-Phosphate Receptors

Journal of Biological Chemistry ◽

10.1074/jbc.272.38.23703 ◽

1997 ◽

Vol 272 (38) ◽

pp. 23703-23706 ◽

Cited By ~ 15

Author(s):

Qimin Zhang ◽

Per-Olof Berggren ◽

Michael Tally

Keyword(s):

Plasma Membrane ◽

Growth Factor ◽

Insulin Like Growth Factor ◽

Factor Ii ◽

Mannose 6 Phosphate

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

Bioscience Reports ◽

10.1007/s10540-006-9013-0 ◽

2006 ◽

Vol 26 (2) ◽

pp. 101-112 ◽

Cited By ~ 9

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.

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