Abstract
Phogrin (IA2-beta) is an integral membrane protein of dense-core vesicles in neuroendocrine cells. We have examined the recycling of endogenous phogrin following exocytosis in insulin secreting Min6 beta-cells by monitoring stimulus dependent-uptake of antibodies directed against the lumenal domain of the protein. While low levels of internalized phogrin accumulated in LAMP1-positive lysosomes, more than 35% of internalized phogrin recycled back to an insulin-positive compartment and could return to the cell surface during a second exocytic stimulation. The recycling phogrin transited a syntaxin 6-positive compartment but did not appear to go through the TGN38-positive trans Golgi network. The results suggest a model in which secretory membrane components can recycle from the endosomal system to immature secretory granules without interaction with the major portion of the TGN.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Line
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Cell Membrane / metabolism
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Chickens
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Endocytosis
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Exocytosis
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Golgi Apparatus / metabolism*
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Image Processing, Computer-Assisted
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Insulin / metabolism*
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Islets of Langerhans / metabolism*
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Lysosomal Membrane Proteins
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Lysosomes / metabolism
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Membrane Glycoproteins / chemistry
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Membrane Glycoproteins / metabolism
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Membrane Proteins / chemistry
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Membrane Proteins / metabolism
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Mice
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Microscopy, Fluorescence
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Protein Structure, Tertiary
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Protein Tyrosine Phosphatases / chemistry
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Qa-SNARE Proteins
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Rabbits
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Receptor-Like Protein Tyrosine Phosphatases, Class 8
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Time Factors
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trans-Golgi Network / metabolism
Substances
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Insulin
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LAMP1 protein, human
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Lysosomal Membrane Proteins
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Membrane Glycoproteins
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Membrane Proteins
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Qa-SNARE Proteins
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Tgoln1 protein, mouse
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Tgoln2 protein, mouse
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PTPRN2 protein, human
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Protein Tyrosine Phosphatases
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Receptor-Like Protein Tyrosine Phosphatases, Class 8