Association of the hepatic IP3 receptor with the plasma membrane: relevance to mode of action

1993 ◽  
Vol 265 (6) ◽  
pp. C1588-C1596 ◽  
Author(s):  
L. Feng ◽  
N. Kraus-Friedmann

Studies were carried out to characterize the interaction between inositol 1,4,5-trisphosphate (IP3) receptors and the plasma membrane fraction. Extraction of the membranes with the nonionic detergents Nonidet P-40 and Triton X-100, followed by centrifugation at 100,000 g, resulted in the doubling of the IP3 receptor in the pellets, whereas no detectable binding was found in the supernatants. These data indicate that the detergents did not solubilize the receptor, that it remained associated with membrane particles, and that it is likely to be associated with the cytoskeleton. The cytoskeleton proteins actin, ankyrin, and spectrin were identified in the plasma membrane fraction. However, comparison of the amount of these proteins in different fractions of the detergent, or otherwise treated plasma membrane fractions, showed no direct correlation between the presence of any of these proteins in the plasma membrane fraction and their ability to bind [3H]IP3. This is in contrast to the brain and T-lymphoma cells in which the IP3 receptor is attached to ankyrin (L. Y. W. Bourguigon, H. Jin, N. Iida, N. R. Brandt, and S. H. Zhang. J. Biol. Chem. 268: 6477-6486, 1993; and S. K. Joseph and S. Samanta. J. Biol. Chem 268: 6477-6486, 1993). Thus the hepatic IP3 receptor, which is different from the brain receptor, might attach to the cytoskeleton by anchoring to a different protein. Because cytochalasin D treatment of livers diminishes the ability of IP3 to raise cytosolic free Ca2+ levels, the attachment of the IP3 receptor to the cytoskeleton seems to involve an association with microfilaments.

1990 ◽  
Vol 1025 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Joseph W. Francis ◽  
James E. Smolen ◽  
Kenneth J. Balazovich ◽  
Rebecca R. Sandborg ◽  
Laurence A. Boxer

1989 ◽  
Vol 109 (4) ◽  
pp. 1519-1528 ◽  
Author(s):  
H Miyata ◽  
B Bowers ◽  
E D Korn

Myosin I accounted for approximately 2% of the protein of highly purified plasma membranes, which represents about a tenfold enrichment over its concentration in the total cell homogenate. This localization is consistent with immunofluorescence analysis of cells that shows myosin I at or near the plasma membrane as well as diffusely distributed in the cytoplasm with no apparent association with cytoplasmic organelles or vesicles identifiable at the level of light microscopy. Myosin II was not detected in the purified plasma membrane fraction. Although actin was present in about a tenfold molar excess relative to myosin I, several lines of evidence suggest that the principal linkage of myosin I with the plasma membrane is not through F-actin: (a) KI extracted much more actin than myosin I from the plasma membrane fraction; (b) higher ionic strength was required to solubilize the membrane-bound myosin I than to dissociate a complex of purified myosin I and F-actin; and (c) added purified myosin I bound to KI-extracted plasma membranes in a saturable manner with maximum binding four- to fivefold greater than the actin content and with much greater affinity than for pure F-actin (apparent KD of 30-50 nM vs. 10-40 microM in 0.1 M KCl plus 2 mM MgATP). Thus, neither the MgATP-sensitive actin-binding site in the NH2-terminal end of the myosin I heavy chain nor the MgATP-insensitive actin-binding site in the COOH-terminal end of the heavy chain appeared to be the principal mechanism of binding of myosin I to plasma membranes through F-actin. Furthermore, the MgATP-sensitive actin-binding site of membrane-bound myosin I was still available to bind added F-actin. However, the MgATP-insensitive actin-binding site appeared to be unable to bind added F-actin, suggesting that the membrane-binding site is near enough to this site to block sterically its interaction with actin.


1978 ◽  
Vol 77 (2) ◽  
pp. 448-463 ◽  
Author(s):  
E Costantino-Ceccarini ◽  
PM Novikoff ◽  
PH Atkinson ◽  
AB Novikoff

A plasma membrane fraction of HeLa S3 cells, consisting of ghosts, is characterized more fully. A simple procedure is described which permits light and electron microscope study of the plasma membrane fraction through the entire depth of the final product pellet and through large areas parallel to the surface. Contamination by nuclei is 0.14%, too little for DNA detection by the diphenylamine reaction. Contamination by rough endoplasmic reticulum and ribosomes is small, a single ghost containing about 3% of the RNA in a single cell. Mitochondria were not encountered. Electron microscopy also shows (a) small vesicles associated with the outer surface of the ghosts, and (b) a filamentous web at the inner face of the ghost membrane. Sodium dodecyl sulfate (SDS)-polyacrylamide gel analysis shows that of the many Coomassie Blue-stained bands two were prominent. One, 43,000 daltons, co-migrated with purified rabbit muscle actin and constituted about 7.5% of the plasma membrane protein. The other major band, 34,000 daltons, was concentrated in the plasma membrane fraction. Two major glycoproteins detected by autoradiography of [14C]fucose-labeled glycoproteins on the gels, had apparent molecular weights of 35,000 daltons and 32,000 daltons. These major bands did not stain with Coomassie Blue. There were many other minor glycoprotein bands in the 200,000- to 80,000-dalton range. Ouabain-sensitive, Na+, K+-adenosine triphosphatase (ATPase) activity of the ghost fraction is purified 9.1 (+/- 2.2) times over the homogenate; recover of the activity is 12.0 (+/- 3.8%) of the homogenate. Enrichment and recovery of fucosylglycoprotein parallel those for ouabain-sensitive Na+, K+-ATPase activity. Fucosyl glycoprotein is recovered more than the enzyme activity in a smooth membrane vesicle fraction probably containing the bulk of plasma membrane not recovered as ghosts.


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