PCP's Research Interests

My primary interest is the development of the nervous system, especially the identification of molecular markers and correlates of cell-fate determination, axonal pathfinding, and synapse formation and regulation. To this end, I have studied the expression, regulation, and function of synaptic components. As an undergraduate, I purified and characterized type II Ca²⁺/calmodulin-dependent protein kinase from Drosophila melanogaster as groundwork for exploiting the ease of genetic manipulation in Drosophila to study further the regulatory properties of the kinase. During my graduate career, key studies included the pharmacological and functional characterization of nicotinic acetylcholine receptors (nAChRs) that bind the snake neurotoxin, [alpha]-bungarotoxin ([alpha]-Bgt), on neurons. The predominantly extra-synaptic nature of such receptors ([alpha]-Bgt-AChRs) has led to the question of whether these nAChRs might be involved in the development and modulation of synapses rather than directly gating synaptic transmission. These experiments demonstrated that [alpha]-Bgt-AChRs could be pharmacologically distinguished from other neuronal nAChRs using several ligands. Using these specific ligands as tools, I showed that [alpha]-Bgt-AChRs were capable of influencing neurite outgrowth in the chick ciliary ganglion (CG): activation of [alpha]-Bgt-AChRs produced the retraction of regenerating neurites dependent on the influx of Ca²⁺ and the activation of voltage-dependent Ca²⁺ channels. The application of monoclonal antibodies made against nAChR subunits to probe the composition of [alpha]-Bgt-AChRs in the CG revealed a second class of components capable of binding [alpha]-Bgt that contain none of the known nAChR gene products.

Work I have done in the bullfrog autonomic nervous system suggests that nAChRs are capable of playing a modulatory role in synaptic transmission. Further, I examined the nAChRs in the chick spinal cord, where I had previously shown the presence of [alpha]-Bgt-AChRs containing the [alpha]-7 gene product. Blockade of nAChR function during chick embryonic development rescues a population of motor neurons from death. Previous studies had suggested that this rescue was the result of the cessation of muscular activity; however, more recent results suggest that montorneurons might be saved even without paralysis. I studied the role that the nAChRs on the motor neurons might play in this phenomenon as well as what role they might play in the initial outgrowth of the motor neurons to their target muscles. Using the more specific drugs which I had characterized during my graduate work, I confirmed that the blockade of muscle receptors was both necessary and sufficient for the promotion of motorneuronal survival. Blockade of the receptors on the neurons themselves was capable of rescuing some of the motorneurons but not the whole population.

Currently, I am investigating the properties of nicotinic receptors which are not at synapses. One question here is what are receptors doing in places where they supposedly will not see agonists. To investigate this, I am developing a new tissue culture system of non-neuronal cells which naturally express the receptors. Using calcium-activated fluorescence, I am investigating whether these receptors can be activated by exposure to nicotine. Further, with Joseph Margiotta, I am investigating some of the mechanisms of receptor clustering on neurons.

You can trace these interest through my publications:

Refereed Papers:

1. Cho, K.-O., J. B. Wall, P. C. Pugh, M. Ito, S. A. Mueller, and M. B. Kennedy. 1991. The [alpha] subunit of type II Ca2+/calmodulin-dependent protein kinase is highly conserved in Drosophila. Neuron 7:439-50.
2. Vijayaraghavan, S., P. C. Pugh, Z.-w. Zhang, M. M. Rathouz, and D. K. Berg. 1992. Nicotinic receptors that bind [alpha]-bungarotoxin on neurons raise intracellular free Ca2+. Neuron 8:353-62.
3. Pugh, P. C., and D. K. Berg. 1994. Neuronal acetylcholine receptors that bind [alpha]-bungarotoxin mediate neurite retraction in a calcium-dependent manner. The Journal of Neuroscience 14:889-96.
4. Pugh, P. C., R. A. Corriveau, W. G. Conroy, and D. K. Berg. 1995. A novel subpopulation of neuronal acetylcholine receptors among those binding [alpha]-bungarotoxin. Molecular Pharmacology 47:717-25.
5. Romano, S. J., P. C. Pugh, J. M. McIntosh, and D. K. Berg. Regulation of neuronal-type acetylcholine receptors containing the [alpha]-7 gene product in vertebrate skeletal muscle. Journal of Neurobiology 32:69-80.
6. Pugh, P.C., P. Jobling, W.-X. Shen, and J. P. Horn Nicotinic modulation of peptidergic transmission in sympathetic ganglia. manuscript in preparation.
7. Pugh, P.C., and E Frank Relative importance of neuronal and muscle nicotinic acetylcholine receptors in survival of spinal motoneurons. manuscript in preparation.

Conference Papers:

1. Berg, D. K., Z.-w. Zhang, W. G. Conroy, P. C. Pugh, R. A. Corriveau, S. J. Romano, B. Huang, and S. Vijayaraghavan. 1995. Expression, function and regulation of neuronal acetylcholine receptors containing the [alpha]-7 gene product. In The effects of nicotine on biological systems II, ed. by P. Clarke, M. Quik, K. Thurau, and F. Adlkofer, (Basel: Birkhäuser), pp. 61-71.
2. Berg, D. K., W. G. Conroy, R. A. Corriveau, P. C. Pugh, M. M. Rathouz, S. J. Romano, S. Vijayaraghavan, and Z.-w. Zhang. Properties of [alpha]-7-containing acetylcholine receptors and their expression in both neurons and muscle. In Proceedings of the 5th International Neuromuscular Meeting, ed. K. Fukushima. (in press).

Abstracts:

1. Leonard, D. S., J. B. Wall, P. C. Pugh, and M. B. Kennedy. 1987. Type II Ca2+/calmodulin-dependent protein kinase in Drosophila. Society for Neuroscience Abstracts 13:154.9.
2. Vijayaraghavan, S., M. M. Rathouz, P. C. Pugh, and D. K. Berg. 1991. Nicotinic receptors that bind [alpha]-bungarotoxin on neurons raise intracellular free Ca2+. Society for Neuroscience Abstracts 17:14.10.
3. Berg, D. K., S. Vijayaraghavan, W. G. Conroy, A. B. Vernallis, R. A. Corriveau, P. C. Pugh, and Z.-W. Zhang. 1992. Native acetylcholine receptors in neurons: Composition, function, and regulation by cell-cell interactions. Journal of Cellular Biochemistry , Supplement 0 16E:218.
4. Pugh, P. C., and D. K. Berg. 1993. Neuronal ACh receptors that bind [alpha]-Bgt mediate neurite retraction in a calcium-dependent manner. Society for Neuroscience Abstracts 19:195.4.
5. Pugh, P. C., R. A. Corriveau, and D. K. Berg. 1994. A subpopulation of neuronal ACh receptors among those binding [alpha]-bungarotoxin. Society for Neuroscience Abstracts 20:466.10.
6. Berg, D. K., W. G. Conroy,,P. C. Pugh, M. M. Rathouz, S. J. Romano, S. Vijayaraghavan, and Z.-W. Zhang. 1995. Co-expression of multiple acetylcholine receptors defined by distinctive subunit composition in neurons and a comparison of functional properties. Journal of Cellular Biochemistry , Supplement 0 19B:170.
7. Berg, D. K., W. G. Conroy, P. C. Pugh, M. M. Rathouz, S. J. Romano, S. Vijayaraghavan, and Z.-W. Zhang. 1995. Neurons co-express multiple heteromeric nicotinic acetylcholine receptors with distinctive subunit compositions: Implications for function. Journal of Neurochemistry 64 (Suppl. 1):S28.
8. Pugh, P. C. and E. Frank. 1997. Nicotinic acetylcholine receptors which bind [alpha]-bungarotoxin on spinal motoneurons. Society for Neuroscience Abstracts 23:461.2.

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