Differential association of rat liver heparan sulfate proteoglycans in membranes of the Golgi apparatus and the plasma membrane
Heparan sulfate proteoglycans (HSPG) of rat liver are associated with the plasma membrane in a hydrophobic intrinsic and a hydrophilic extrinsic form. We were interested in determining whether or not these two forms could be detected in the Golgi apparatus, the subcellular site of addition of oligosaccharides and sulfate to HSPG. In vivo and in vitro radiolabeled HSPG from rat liver Golgi apparatus membranes could only be solubilized with detergents that disrupt the membrane lipid bilayer, suggesting that they are solely associated via hydrophobic interactions. Both forms of HSPG were detected in plasma membranes of rat liver and isolated rat hepatocytes. The detergent-solubilized HSPG bound to octyl-Sepharose columns, whereas the hydrophilic form did not; this latter form, however, was released from the membrane by heparin. The hydrophobic anchor of HSPG in the Golgi and plasma membranes was insensitive to treatment with phosphatidylinositol-specific phospholipase C under conditions in which alkaline phosphatase was sensitive; this suggests that the hydrophobic anchor of HSPG is the core protein itself. Preliminary experiments suggest that the subcellular site of processing of the hydrophobic to the hydrophilic form of HSPG is the plasma membrane. A specific processing activity, probably a protease of the plasma membrane not present in serum or the endoplasmic reticulum membrane, converted hydrophobic HSPG of the Golgi membrane to the hydrophilic form. In addition, pulse-chase experiments with (35S)Na2SO4 in rats demonstrated that at short times, the bulk of the radiolabeled cellular HSPG was in the Golgi apparatus; later on, the bulk of the radioactivity was found in the plasma membrane, the only subcellular site where the hydrophilic form of HSPG was detected.
- Research Organization:
- Catholic Univ. of Chile, Santiago
- OSTI ID:
- 5768380
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 264:18
- Country of Publication:
- United States
- Language:
- English
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GLYCOPROTEINS
SUBCELLULAR DISTRIBUTION
BIOCHEMICAL REACTION KINETICS
CELL MEMBRANES
CHONDROITIN
HEPARIN
LIVER
ORGANOIDS
PEPTIDE HYDROLASES
POLYSACCHARIDES
RATS
SULFATES
SULFUR 35
TRACER TECHNIQUES
AMINES
ANIMALS
ANTICOAGULANTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CARBOHYDRATES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DISTRIBUTION
DRUGS
ENZYMES
EVEN-ODD NUCLEI
GLANDS
HEMATOLOGIC AGENTS
HYDROLASES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAMMALS
MEMBRANES
MUCOPOLYSACCHARIDES
NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
OXYGEN COMPOUNDS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
SACCHARIDES
SULFUR COMPOUNDS
SULFUR ISOTOPES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques