This project addresses a general problem of synaptic physiology, the role played by both heterotrimeric GTP-binding proteins (G-proteins) and phosphorylation cascades in transducing the slow electrical actions of transmitters. In the neuroblastoma-glioma cell line (NG108-15), a model neuron used in this project, the neuropeptide bradykinin (BK) has a dual action, activation of a K+ current, and inhibition of the voltage-dependent Ca2+ current, ICa V. These two effects of BK are mediated by distinct G-proteins, both insensitive to pertussis toxin (PTX): the G-protein Gq/11 mediates the activation of K+ current, while G13 mediates the inhibition of the ICa V. What is the mechanism of the action of these two G-proteins on the ion channels they modulate? At least part of the action of Gq/11 is via activation of phospholipase C (PI-PLC) and release of IP3, which in turn raises intracellular Ca2+ and activates Ca2+ -dependent K+ channels. The mechanism of action of G13 is not known. Preliminary observations from the PI's laboratory indicate that the ion channel regulatory actions of both Gq/11 and G13 are transduced by phosphorylation cascade(s). Furthermore, there are indications that these cascades require activation of mitogen-activated protein kinases (MAPKs), a family of kinases which transduce the effects of hormones, growth factors and transmitters. Thus, this project aims to determine the organization of the phosphorylation pathways activated by Gq/11 and G13, to probe the coupling between G-proteins and their cascades, and to investigate the relationship between the phosphorylation pathways and the PI- PLC/IP3/Ca2+ pathway.
These aims will be achieved by combining patch- clamp recording of the electrical responses to BK with intracellular perfusion of specific reagents, including constitutively active or inactive kinases, G-proteins and enzyme inhibitors. While BK is an important mediator of pain and inflammation, in general G-protein- coupled receptors transduce the actions of numerous neurotransmitters, hormones and drugs. Thus this project is relevant for understanding and treating diseases of both the central nervous system and the peripheral tissues.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM047721-05
Application #
2415168
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1992-05-01
Project End
2000-04-30
Budget Start
1997-05-01
Budget End
1998-04-30
Support Year
5
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
City
Dallas
State
TX
Country
United States
Zip Code
75390
Wilk-Blaszczak, M A; Stein, B; Xu, S et al. (1998) The mitogen-activated protein kinase p38-2 is necessary for the inhibition of N-type calcium current by bradykinin. J Neurosci 18:112-8
Wilk-Blaszczak, M A; Singer, W D; Quill, T et al. (1997) The monomeric G-proteins Rac1 and/or Cdc42 are required for the inhibition of voltage-dependent calcium current by bradykinin. J Neurosci 17:4094-100
Wilk-Blaszczak, M A; Singer, W D; Belardetti, F (1996) Three distinct G protein pathways mediate inhibition of neuronal calcium current by bradykinin. J Neurophysiol 76:3559-62
Horstman, D A; Ball, R; Carpenter, G (1995) Baculovirus expression and purification of the second messenger enzyme phospholipase C-gamma 1, a tyrosine kinase substrate. Protein Expr Purif 6:278-83
Wilk-Blaszczak, M A; Gutowski, S; Sternweis, P C et al. (1994) Bradykinin modulates potassium and calcium currents in neuroblastoma hybrid cells via different pertussis toxin-insensitive pathways. Neuron 12:109-16
Wilk-Blaszczak, M A; Singer, W D; Gutowski, S et al. (1994) The G protein G13 mediates inhibition of voltage-dependent calcium current by bradykinin. Neuron 13:1215-24
Kuo, W N; Dominguez, J L; Shabazz, K A et al. (1986) Modulation of the catalytic subunit of cyclic AMP-dependent protein kinase by calmodulin, S-100 protein, parvalbumin and troponin. Cytobios 46:139-46
Kuo, W N; Rahmani, M A; Blake, T et al. (1986) Probable occurrence of brain basic protein factor I, an activator of phosphoprotein phosphatases. Cytobios 47:45-52