H. Clive Palfrey, Ph.D.

Professor, Neurobiology, Pharmacology and Physiology

Committee on Cancer Biology
Committee on Cellular and Molecular Physiology

Research Summary

Research in my laboratory is centered around signalling events, particularly those that involve intracellular Ca2+ and the major Ca2+ -binding regulatory protein calmodulin. Two systems we are investigating are the regulation of protein synthesis and the control of endocytosis by Ca2+, both of which involve (different) calmodulin-regulated events. We are also interested in the mechanism of action of neurotrophic factors like nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) as they relate to the effects of these proteins on CNS neurons. Part of the action of these factors also involves Ca2+.

Current projects include:

Neurotrophic factors and CNS neurons

We have shown that primary cultures of rat embryonic hippocampal neurons can be used for biochemical investigations of the signal transduction pathways activated by BDNF and neurotrophin-3. These cells homogeneously express the receptors for these neurotrophins (receptor tyrosine kinases called TrkB and TrkC), and respond uniformly with various signalling events including elevations of intracellular [Ca2+], ras and MAP kinase activation. We are presently invetigating the relationship of various signalling pathways to survival in neurons: which pathways are important and are they the same in each cell type? These kinds of questions ultimately relate to the function of neurons in degenerative diseases and aging where neurotrophic factors have been suggested as possible ameliorative agents.

Calmodulin dependent protein kinases and protein translation

Protein phosphorylation systems are central to the operation of virtually all signalling cascades. In order to understand in detail how signals are transduced, an intimate knowledge of specific protein kinases and their targets is required. Another set of investigations in my laboratory centers around the family of enzymes known as calmodulin-dependent protein kinases. These enzymes are important in transducing intracellular Ca signals, generated by a variety of hormones and neurotransmitters, into physiological changes in the cell by phosphorylating key substrates. One such system is that involving calmodulin-dependent protein kinase III and its only substrate elongation factor-2 (EF-2). EF-2 is a critical factor in protein synthesis; phosphorylation by the kinase at a single threonine prevents its participation in protein synthesis in vitro. We are examining a number of systems to evaluate the physiological role of this phosphorylation process. It seems to play a critical role in the cell cycle, particularly on exit from quiescence.

Rapid endocytosis and its regulation: calmodulin and dynamin

Endocytosis is the mechanism by which secretory cells recover vesicular membrane after secretion. We showed that this mechanism is distinct from receptor-mediated endocytosis and that it is dependent on a distinct isoform of the protein dynamin. Dynamin is a 100 kDa GTPase that seems to be involved in the "pinch-off" step whereby retracting endosomes are severed from the plasma membrane. The process also requires calmodulin and we are determining the regulatory steps that are controlled by these proteins.

Selected Publications

Updated 12/18/02.