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High- and low-affinity CCKA receptor states mediate specific growth inhibitory effects on CHO cells
K Detjen1, M J Tseng, C D Logsdon
1Department of Physiology, University of Michigan, Ann Arbor 48109-0622, USA.
Abstract:
To relate specific effects on growth and transformation to activation of specific affinity states of the CCKA receptor stably expressed in CHO cells we compared responses to the CCK analogues JMV-180 and CCK8. CCK8 led to an inhibition of both cell proliferation and transformation. Effects on proliferation were indicated by a reduction of DNA synthesis and cell numbers. Effects on transformation were indicated by a reduction of colony formation in soft-agar. JMV-180 did not inhibit cell proliferation although a small inhibitory effect on DNA synthesis was observed. JMV-180 inhibited the maximal effects of CCK8 on cell proliferation and DNA synthesis. In contrast, JMV-180 substantially inhibited cell colony formation in soft-agar and did not inhibit the effects of CCK8 on this parameter. Collectively these data with receptor affinity state specific analogues indicated that inhibition of cell proliferation and growth in soft-agar can be attributed to activation of distinct affinity states. Thus, different second messengers are likely responsible for the inhibitory effects on anchorage-dependent and -independent growth.
Insights
CCK8 inhibits cell proliferation and transformation by activating specific CCKA receptor states. JMV-180, a CCKA receptor analogue, selectively inhibits transformation, suggesting distinct pathways regulate growth and anchorage-independent growth.
Area of Science:
- Cell Biology
- Molecular Pharmacology
Background:
- The cholecystokinin A receptor (CCKA) plays a role in cell growth and transformation.
- Understanding CCKA receptor signaling is crucial for cancer research.
Purpose of the Study:
- To investigate the relationship between CCKA receptor affinity states and cellular responses.
- To differentiate the effects of CCK8 and JMV-180 on cell proliferation and transformation.
Main Methods:
- Stable expression of CCKA receptor in Chinese Hamster Ovary (CHO) cells.
- Treatment with CCK8 and JMV-180 analogues.
- Assessment of cell proliferation (DNA synthesis, cell numbers) and transformation (soft-agar colony formation).
Main Results:
- CCK8 inhibited both cell proliferation and soft-agar colony formation.
- JMV-180 showed minimal effect on proliferation but significantly inhibited soft-agar colony formation.
- JMV-180 modulated CCK8's effects on proliferation but not on transformation.
Conclusions:
- Activation of distinct CCKA receptor affinity states mediates differential effects on cell proliferation and anchorage-independent growth.
- Separate second messenger pathways likely underlie the regulation of anchorage-dependent and -independent growth by CCKA receptor activation.