Role of plasma membranes in stimulation of RNA-directed DNA synthesis

Nature ◽  
1976 ◽  
Vol 262 (5571) ◽  
pp. 805-807 ◽  
Author(s):  
L. C. PADHY ◽  
S. K. KAR ◽  
K. K. RAO ◽  
M. R. DAS
Keyword(s):  
Dna Synthesis ◽  
Plasma Membranes ◽  
Stimulation Of

The biological activity of glucagon–phospholipid complexes

1983 ◽  
Vol 61 (7) ◽  
pp. 688-691 ◽  
Author(s):  
J. J. Liepnieks ◽  
P. Stoskopf ◽  
E. A. Carrey ◽  
C. Prosser ◽  
R. M. Epand
Keyword(s):  
Biological Activity ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Bovine Brain ◽  
Water Soluble ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Dimyristoyl Phosphatidylcholine ◽  
Lipoprotein Complex ◽  
Stimulation Of

Glucagon can form water-soluble complexes with phospholipids. The incorporation of glucagon into these lipoprotein particles reduces the biological activity of the hormone. The effect is observed only at temperatures below the phase transition temperature of the phospholipid and results in a decreased stimulation of the adenylate cyclase of rat liver plasma membranes by the lipoprotein complex as compared with the hormone in free solution. Two- to five-fold higher concentrations of glucagon are required for half-maximal stimulation of adenylate cyclase when the hormone is complexed with dimyristoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine, or bovine brain sphingomyelin. A possible role of lipoprotein-associated hormones in the development of insulin resistance is discussed.

Role of polyamines in glucocorticoid effects on pancreatic acinar AR42J cell growth and differentiation

1992 ◽  
Vol 262 (2) ◽  
pp. G285-G290
Author(s):  
C. D. Logsdon ◽  
F. Alves ◽  
S. Rosewicz
Keyword(s):  
Cell Growth ◽  
Dna Synthesis ◽  
Mrna Levels ◽  
Ar42j Cells ◽  
Glucocorticoid Induction ◽  
Cell Growth And Differentiation ◽  
Ar42j Cell ◽  
Inhibition Of Dna Synthesis ◽  
Stimulation Of

We previously found that glucocorticoids inhibit growth and increase differentiation in rat pancreatic acinar AR42J cells. In the current study, we examined the role of polyamines in these effects. Treatment of AR42J cells with the ornithine decarboxylase (ODC) inhibitor difluoromethylornithine (DFMO) inhibited DNA synthesis. Thus polyamines are required for AR42J cell growth. However, we have previously shown that dexamethasone (Dex) increased AR42J cell ODC activity and mRNA levels. In the current study, we found that Dex treatment increased cellular putrescine levels. These increases in ODC and putrescine occurred during Dex-induced inhibition of DNA synthesis. Therefore, in AR42J cells, ODC activity and polyamine levels are not strictly growth related. To examine the requirement for glucocorticoid induction of ODC activity in glucocorticoid stimulation of differentiation, we examined the effects of DFMO on amylase gene expression and cholecystokinin binding. DFMO reduced cell amylase content while having little effect on mRNA levels in both Dex-treated and untreated cells. In contrast, DFMO had little effect on control CCK binding but inhibited the Dex-induced increase. Thus polyamines are necessary for growth and glucocorticoid-induced differentiation of AR42J cells; however, effects of glucocorticoids on AR42J cell growth and differentiation are not mediated by effects on ODC.

scholarly journals Extracellular Na+ and initiation of DNA synthesis: role of intracellular pH and K+.

1984 ◽  
Vol 98 (3) ◽  
pp. 1082-1089 ◽  
Author(s):  
C P Burns ◽  
E Rozengurt
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Dna Synthesis ◽  
Cellular Proliferation ◽  
Weak Acid ◽  
Mechanisms Of Action ◽  
Epidermal Growth ◽  
Reversible Time ◽  
Stimulation Of

Initiation of DNA synthesis in confluent quiescent 3T3 cell cultures stimulated by epidermal growth factor (EGF), vasopressin, and insulin was abolished by removing extracellular Na+. The inhibition was reversible, time- and Na+-concentration-dependent, and not due to an effect on binding or internalization of 125I-EGF. Stimulation by combinations of other growth factors with different mechanisms of action was also affected by decreasing extracellular Na+, but with different half-maximal Na+ concentrations. When choline was used as an osmotic substitute for Na+, the decrease in DNA synthesis was correlated with the decrease in intracellular K+. In contrast, when sucrose was used there was stimulation of the Na+-K+ pump and maintenance of intracellular K+ that resulted in a somewhat higher rate of DNA synthesis at lowered extracellular Na+ compared to choline. Mitogenesis induced by epidermal growth factor, vasopressin, and insulin led to cytoplasmic alkalinization as determined by an increase in uptake of the weak acid 5,5-dimethyloxazolidine-2,4-dione. Experimental decrease in extracellular Na+ blocked this cellular alkalinization. Therefore, under some conditions the supply of extracellular Na+ may limit cellular proliferation because of a reduction in the provision of Na+ to the Na+/H+ antiport and resultant failure of alkalinization. We conclude that Na+ flux and its effect on intracellular K and pH has a major role in the complex system that regulates proliferation.

Stimulation of DNA synthesis in senescent human cells following incubation with plasma membranes

1992 ◽  
Vol 202 (2) ◽  
pp. 386-390 ◽  
Author(s):  
Katherine B. Frederich ◽  
Paul D. Phillips ◽  
Vincent J. Cristofalo
Keyword(s):  
Dna Synthesis ◽  
Plasma Membranes ◽  
Human Cells ◽  
Stimulation Of

scholarly journals Stimulation of exocytotic membrane fusion by modified peptides of the rab3 effector domain: re-evaluation of the role of rab3 in regulated exocytosis

1993 ◽  
Vol 294 (2) ◽  
pp. 325-328 ◽  
Author(s):  
C M MacLean ◽  
G J Law ◽  
J M Edwardson
Keyword(s):  
Membrane Fusion ◽  
Plasma Membranes ◽  
Zymogen Granule ◽  
Zymogen Granules ◽  
Fusion Event ◽  
Effector Domain ◽  
Granule Membrane ◽  
Modified Peptides ◽  
Stimulation Of

We have shown previously that fusion between pancreatic zymogen granules and plasma membranes is stimulated by a peptide corresponding to the putative effector domain of rab3. Here we show that this stimulatory effect persists when the amino acid sequence of the peptide is substantially modified. We also show that an antibody raised against rab3a recognizes a protein of appropriate size on the zymogen-granule membrane, but has no effect on membrane fusion. We suggest that rab3 is not directly involved in the control of this membrane fusion event, and that the peptides are stimulating fusion by a mechanism unrelated to rab3.

scholarly journals Purified plasma membranes inhibit polypeptide growth factor-induced DNA synthesis in subconfluent 3T3 cells.

1984 ◽  
Vol 98 (3) ◽  
pp. 1129-1132 ◽  
Author(s):  
R D Vale ◽  
S W Peterson ◽  
N V Matiuck ◽  
C F Fox
Keyword(s):  
Growth Factor ◽  
Dna Synthesis ◽  
Plasma Membranes ◽  
3T3 Cells ◽  
Surface Receptors ◽  
Polypeptide Growth Factors ◽  
Polypeptide Growth Factor ◽  
Epidermal Growth ◽  
High Concentrations ◽  
Stimulation Of

Plasma membranes derived from NR-6 cells, a variant line of Swiss mouse 3T3 cells that does not have cell surface receptors for epidermal growth factor (EGF), inhibited EGF-induced stimulation of DNA synthesis by 50% in serum-starved, subconfluent 3T3 cells. Membranes derived from SV3T3 cells were much less effective in inhibiting EGF-induced DNA synthesis. This inhibition on DNA synthesis by NR-6 membranes was not a direct effect of membranes on EGF, nor could it be overcome by high concentrations of EGF. NR-6 membranes were most effective when added 3 h before EGF addition and had little effect when added 2 h or more after EGF. NR-6 membranes also reduced the stimulation of DNA synthesis induced by platelet-derived growth factor or fibroblast growth factor in serum-starved 3T3 cells. These findings indicate that membrane-membrane interactions between nontransformed cells may diminish their ability to proliferate in response to serum polypeptide growth factors.

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