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C Rim

Publications and source records attributed to C Rim.

11 recordsLinked to original sources
PubMed1995

Cyclic adenosine monophosphate can convert epidermal growth factor into a differentiating factor in neuronal cells.

The rat pheochromocytoma (PC12) cell line is a model for studying the mechanism of growth factor action. Both epidermal growth factor and nerve growth factor stimulate mitogen-activated protein (MAP) kinase in these cells. Recent data suggest that the transient activation of MAP kinase may trigger proliferation, whereas sustained activation triggers differentiation in these cells. We have tested this model by asking whether agents that stimulate MAP kinase without inducing differentiation can act additively to trigger differentiation. Neither forskolin nor epidermal growth factor can stimulate differentiation, yet both activate MAP kinase in these cells. Together, their actions on MAP kinase are synergistic. Cells treated with both agents differentiate, measured morphologically and by the induction of neural-specific genes. We propose that cellular responses to growth factor action are dependent not only on the activation of growth factor receptors by specific growth factors but on synchronous signals that may elevate MAP kinase levels within the same cells.

Adrenal Gland Neoplasms↗
PubMed1994

The somatostatin receptor SSTR1 is coupled to phosphotyrosine phosphatase activity in CHO-K1 cells.

Somatostatin receptors are abundantly expressed on a variety of human endocrine and epithelial tumors. The ability of these receptors to couple to effector pathways that inhibit the growth of these tumor cells has prompted the use of somatostatin agonists in the treatment of human neoplasms. It has been demonstrated that somatostatin stimulates a phosphotyrosine phosphatase in human tumor cells through a receptor-mediated process. This stimulation may counteract the growth-promoting properties of growth factors and the receptor tyrosine kinases that they activate. The recent cloning and characterization of distinct somatostatin receptor subtypes raise the possibility that different receptor subtypes mediate distinct effector pathways. To determine whether cloned somatostatin receptors could mediate coupling to phosphotyrosine phosphotyrosine phosphatase activity, we examined phosphatase activity after somatotostatin activation of the rat somatostatin receptors SSTR1 and SSTR2 after their stable expression in heterologous Chinese Hamster Ovary (CHO-K1) cells. We found that stimulation of SSTR1 cells was capable of increasing phosphotyrosine phosphatase activity, despite the coupling of both receptors to the inhibition of adenylyl cyclase in these cells. This activation was characterized by an EC50 of 70 nM and was sensitive to pertussis toxin. In addition, we demonstrate that activation of phosphotyrosine phosphatase activity in pituitary cell lines correlates with the endogenous expression of the SSTR1 gene within these cells.

Adenylate Cyclase Toxin↗
PubMed1993

Cloning and expression of two structurally distinct receptor-linked protein-tyrosine phosphatases generated by RNA processing from a single gene.

We describe here the first example of RNA processing generating two functional receptor-linked protein-tyrosine phosphatases (PTP) (protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) that are structurally distinct within their catalytic domains. Two cDNAs, PTP-P1 and PTP-PS, were isolated from rat pheochromocytoma cells, which encode two receptor-linked protein-tyrosine-phosphatases and are produced by alternative splicing and differential use of polyadenylation sites. Both cDNAs share an identical extracellular domain and a single transmembrane domain, but differ within their cytoplasmic regions: PTP-P1 contains two tandem repeated PTPase catalytic domains, whereas PTP-PS contains only the amino-terminal domain. Bacterial expression of PTPase domains of both cDNAs demonstrates that PTP-P1 and PTP-PS contain tyrosine-phosphatase activity. PTP-P1 is encoded by three transcripts of approximately 8, 6, and 4 kilobases, whereas PTP-PS is encoded by a single 4.8-kilobase transcript. PTP-P1 (6 kilobases) and PTP-PS are mainly expressed within the brain and in neuronal and endocrine cells. These data suggest that PTP-P1 and PTP-PS may be involved in neuronal function.

Alternative Splicing↗
PubMed1992

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Journal Article↗