Tod Gulick, M.D.

My research program applies basic biochemical and cell and molecular biological approaches to address several aspects of mitochondrial function involving gene expression and metabolite transport.

One project involves transport of nucleotides between cytosol and the mitochondrial matrix. The impetus for the project involved a desire to better understand the mitochondrial DNA depletion and associated metabolic disorders that accompany antiviral nucleoside reverse transcriptase inhibitor (NRTI) therapy used in highly active anti-retroviral therapy in AIDS. We identified a set of nucleotide transporters and believe that they provide the major pathway for mitochondrial uptake of nucleotide derivatives of the NRTIs. Various approaches are being applied to understand the constraints on mitochondrial uptake of modified nucleotides by these transporters, with the prospect of identifying antiretroviral nucleoside analogs with lower toxicity.

A second project involves the transcriptional control of genes that encode key enzymes involved in fuel oxidation in muscle. This work has identified a key role for myocyte enhancer factor 2 (MEF2) proteins, as well as an evolutionarily conserved transcriptional network involving nuclear respiratory factor (NRF) control of MEF2 expression. We are using drosophila and transgenic mouse models to better understand the roles of these factors in muscle gene expression relevant to metabolism.

The third project involves MEF2 pre-mRNA alternative splicing, and addresses both the distinct functions of splicing variants and the regulation of splicing isoform expression, toward understanding distinct MEF2 functions among tissues and during development. Among several findings, we have described an evolutionarily conserved autonomous trans-acting repressor domain in MEF2s whose function is controlled by serine modification via the activity of cyclin-dependent kinases (cdk). A regulated alternative splicing event yields a MEF2 variant that excludes this domain, permiting escape from cdk control. We are using gene knock-in mice to explore the roles of splicing variants in muscle development and differentiation and gene expression. We have developed minigenes that selectively report specific MEF2 splicing events toward understanding cis-acting elements, and factors and signals, that control muscle-specific splicing.

References:

1. Yu GS, Lu YC, Gulick T. Co-regulation of tissue-specific alternative human carnitine palmitoyltransferase Ibeta gene promoters by fatty acid enzyme substrate. J Biol Chem. 1998;273:32901-9.

2. Yu GS, Lu YC, Gulick T. Rat carnitine palmitoyltransferase Ibeta mRNA splicing isoforms.Biochim Biophys Acta. 1998;1393:166-72.

3. Kim JY, Koves TR, Yu GS, Gulick T, Cortright RN, Dohm GL, Muoio DM. Evidence of a malonyl-CoA-insensitive carnitine palmitoyltransferase I activity in red skeletal muscle. Am J Physiol Endocrinol Metab. 2002;282:E1014-22.


	Tod Gulick, M.D. Mitochondrial function in muscle My research program applies basic biochemical and cell and molecular biological approaches to address several aspects of mitochondrial function involving gene expression and metabolite transport. One project involves transport of nucleotides between cytosol and the mitochondrial matrix. The impetus for the project involved a desire to better understand the mitochondrial DNA depletion and associated metabolic disorders that accompany antiviral nucleoside reverse transcriptase inhibitor (NRTI) therapy used in highly active anti-retroviral therapy in AIDS. We identified a set of nucleotide transporters and believe that they provide the major pathway for mitochondrial uptake of nucleotide derivatives of the NRTIs. Various approaches are being applied to understand the constraints on mitochondrial uptake of modified nucleotides by these transporters, with the prospect of identifying antiretroviral nucleoside analogs with lower toxicity. A second project involves the transcriptional control of genes that encode key enzymes involved in fuel oxidation in muscle. This work has identified a key role for myocyte enhancer factor 2 (MEF2) proteins, as well as an evolutionarily conserved transcriptional network involving nuclear respiratory factor (NRF) control of MEF2 expression. We are using drosophila and transgenic mouse models to better understand the roles of these factors in muscle gene expression relevant to metabolism. The third project involves MEF2 pre-mRNA alternative splicing, and addresses both the distinct functions of splicing variants and the regulation of splicing isoform expression, toward understanding distinct MEF2 functions among tissues and during development. Among several findings, we have described an evolutionarily conserved autonomous trans-acting repressor domain in MEF2s whose function is controlled by serine modification via the activity of cyclin-dependent kinases (cdk). A regulated alternative splicing event yields a MEF2 variant that excludes this domain, permiting escape from cdk control. We are using gene knock-in mice to explore the roles of splicing variants in muscle development and differentiation and gene expression. We have developed minigenes that selectively report specific MEF2 splicing events toward understanding cis-acting elements, and factors and signals, that control muscle-specific splicing. References: 1. Yu GS, Lu YC, Gulick T. Co-regulation of tissue-specific alternative human carnitine palmitoyltransferase Ibeta gene promoters by fatty acid enzyme substrate. J Biol Chem. 1998;273:32901-9. 2. Yu GS, Lu YC, Gulick T. Rat carnitine palmitoyltransferase Ibeta mRNA splicing isoforms.Biochim Biophys Acta. 1998;1393:166-72. 3. Kim JY, Koves TR, Yu GS, Gulick T, Cortright RN, Dohm GL, Muoio DM. Evidence of a malonyl-CoA-insensitive carnitine palmitoyltransferase I activity in red skeletal muscle. Am J Physiol Endocrinol Metab. 2002;282:E1014-22.