PMID:11083468

Citation	Soltys, BJ, Kang, D and Gupta, RS (2000) Localization of P32 protein (gC1q-R) in mitochondria and at specific extramitochondrial locations in normal tissues. Histochem. Cell Biol. 114:245-55
Abstract	P32 protein, also known as the gC1q receptor for complement component C1q, is a binding protein for nuclear pre-mRNA splicing factor SF2/ASF and numerous other nuclear and cell surface proteins, yet is targeted to the mitochondrial matrix compartment where these proteins are not present. In the present study, we use immunogold electron microscopy to evaluate the subcellular distribution of P32 protein (gC1q-R) in cultured cell lines and in rat tissues embedded in the acrylic resin LR Gold. Immunogold labeling of Raji lymphoma, CHO, human fibroblasts, HeLa and B-SC-1 cells shows reactivity primarily within mitochondria. Highly specific labeling of mitochondria is also obtained in rat tissues, including adrenal gland, cerebellum, cerebral cortex, heart, kidney, liver, pituitary, pancreas, skeletal muscle, spleen, testes and thyroid. However, strong P32 (gClq-R) reactivity is also present in (i) zymogen granules, condensing vacuoles, endoplasmic reticulum, and on the cell surface of pancreatic acinar cells, (ii) on the cell surface of microvascular endothelial cells in pancreas and kidney, (iii) on the cell surface and in nuclei of splenic lymphocytes, and (iv) in the acrosome of developing spermatids in testes. Western immunoblots show that the polyclonal antibody to P32 (gC1q-R) used in this study reacts specifically with a 32-kDa protein in both purified pancreatic zymogen granules and in mitochondria, and no other proteins are reactive. These results provide evidence that P32 (gC1q-R) is a mitochondrial protein that also localizes outside mitochondria in certain cells and tissues under normal physiological conditions.
Links	PubMed
Keywords	Animals; Antigens, CD44; Blotting, Western; Brain/cytology; Burkitt Lymphoma; CHO Cells; Carrier Proteins; Cattle; Cricetinae; Cytoplasmic Granules/ultrastructure; Endothelium, Vascular/ultrastructure; Fibroblasts/cytology; HeLa Cells; Humans; Male; Membrane Glycoproteins; Microscopy, Electron; Microscopy, Immunoelectron; Mitochondria/chemistry; Mitochondria/ultrastructure; Mitochondrial Proteins; Pancreas/ultrastructure; Rats; Receptors, Complement/analysis; Tumor Cells, Cultured
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RAT:C1QBP		GO:0005739: mitochondrion	ECO:0000314:		C		Figure 1	complete CACAO 10532
HUMAN:C1QBP		GO:0005739: mitochondrion	ECO:0000314:		C		Figure 1 in lymphoma cells.	complete CACAO 10538
HUMAN:C1QBP	part_of	GO:0005739: mitochondrion	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete

References

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