Research Interests

Protein phosphatases of Arabidopsis thaliana and human cells
Protein phosphorylation is a dynamic process that regulates almost every aspect of cell biology. The protein kinases and phosphatases, which add and remove phosphate respectively, represent 2-4% of the protein encoding genes of eukaryotes. My research focuses on the protein phosphatases of humans and the model higher plant Arabidopsis thaliana using a combination of biochemistry, molecular biology and bioinformatics. Major projects include the characterization of plant protein phosphatase one (PP1) regulatory subunits, human nuclear PP1 binding proteins and novel chloroplast protein phosphatases. PP1 is enriched in the nucleus of cells, yet very few roles for this enzyme are known in this compartment. Utilizing affinity chromatography of HeLa cell nuclear extracts on microcystin-Sepharose and SILAC mass spectrometry (in collaboration with L. Trinkle-Mulcahy) we have found numerous new PP1 targeting subunits and complexes. Genomics and bioinformatics has revealed a host of novel chloroplast localized protein phosphatases and we are defining the biochemistry and role of several of these enzymes.

My group is also funded by the Alberta Ingenuity Carbohydrate Research Group (AICCS) to explore the role of the chloroplast localized dual-specificity phosphatase SEX4. SEX4 was previously identified in a screen for plant starch excess mutants and has now been found to bind to and dephosphorylate starch. We are currently characterizing the unique redox regulation of the enzyme in response to the light-dark transition.

We are also interested in the interaction and regulation of carbon and nitrogen metabolism in Arabidopsis and we are currently defining the role of the chloroplast-localized protein PII. PII was discovered in bacteria as a key regulator of responses to changes in carbon and nitrogen availability and metabolism. We have determined that plant PII allosterically senses the amino acid carbon skeleton 2-oxoglutarate and the adenylates ADP and ATP. The primary interaction target of plant PII is the enzyme N-acetylglutamate kinase (NAGK) that catalyzes the rate-limiting step in arginine biosynthesis. The docking of PII to NAGK relieves the inhibition that the down stream product arginine has on NAGK. We are currently exploring the possibility that additional protein targets are regulated by PII in the chloroplast.

Courses Taught

Graduate Students

Awards

2006 - University of Calgary International Fellowship
2006 - Canadian Society of Plant Biology CD Nelson prize(outstanding res. contributions as independent investigator for less than 10 years
2005 - Killam Resident Fellowship

Funding

NSERC discovery grant
ACB (Alberta Cancer Board)
Canadian Breast Cancer Foundation

 

Selected publications

• George W. Templeton, Mhairi Nimick, Nicholas Morrice, David Campbell, Marilyn Goudreault, Anne-Claude Gingras, Ken-ichiro Shimazaki and Greg B.G. Moorhead (2011) Identification and characterization of AtI-2, an Arabidopsis homolog of an ancient protein phosphatase 1 (PP1) regulatory subunit. Biochem J 435: 73-83.
• Delphine Chamousset, Veerle DeWever, Yan Chen, Greg Moorhead, Fabien Charriere, Francois-Michel Boisvert, Angus I. Lamond and Laura TrinkleMulcahy (2010) RRP1B targets PP1 to mammalian cell nucleoli and is associated with the pre-60S ribosomal subunit.  Mol Biol Cell 21(23):4212-26.
• David Kerk and Greg B.G. Moorhead (2010) A phylogenetic survey of myotubularin genes of eukaryotes: distribution, evolution, protein structure, and gene expression BMC Evol Biol. 2010 Jun 24;10(1):196.
• Glen Uhrig, KK Ng and Greg B. G. Moorhead (2009) PII in higher plants: a modern role for an ancient protein. Trends in Plant Science 14: 505-11.
• Greg B. G. Moorhead, Veerle De Wever, George Templeton and David Kerk (2009) Evolution of protein phosphatases in plants and animals. Biochem. J 417: 401-409. Invited Review for a special issue of the Biochemical Journal that marks the Darwin Bicentenary. These reviews were made into a special collection in honor of the bicentenary.
  
• Greg B. G. Moorhead, Laura Trinkle-Mulcahy, Mhairi Nimick, Veerle DeWever, David G. Campbell, Robert Gourlay, Yun Wah Lam, Angus I. Lamond. (2008) Displacement affinity chromatography of protein phosphatase one (PP1) complexes. BMC Biochemistry 9:28 (10 November 2008).
  
• David Kerk, George W Templeton, Greg BG Moorhead (2008) Evolutionary pattern of radiation of novel protein phosphatases revealed by analysis of protein data from the completely sequenced genomes of humans, green algae and higher plants. Plant Physiol 146: 351-67.
• Greg B. G. Moorhead, Laura Trinkle-Mulcahy and Anne Ulke-Lemée (2007) Emerging roles of nuclear protein phosphatases. Invited review for Nat Rev Mol Cell Biol  8: 234-44.
  
• Anne Ulke-Lemée, Laura Trinkle-Mulcahy, Steve Chaulk, Nina K Bernstein, Nick Morrice, Mark Glover, Angus I. Lamond and Greg BG Moorhead (2007) The nuclear PP1 interacting protein ZAP is a polynucleotide kinase/phosphatase that complexes with CIA, NF90, SAM68 and hnRNP G  Biochim. Biophys. Acta Proteins and Proteomics 1774:1339-50
  
• Yutaka Muzino, Byron Berenger, Greg B. G. Moorhead and Ken K Ng (2007) Crystal structure of Arabidopsis PII reveals novel structural elements unique to eukaryotes. Biochemistry 46:1477-83.
• Greg B. G. Moorhead, Yan M. Chen, Tony S. Ferrar, Yutaka Mizuno, Catherine S. Smith, Kenneth K.S. Ng, Douglas G. Muench, and Elke Lohmeir-Vogel (2007) The higher plant PII signal transduction protein: structure, function and properties. Invited review for Canadian Journal of Botany to commemorate receiving the CD Nelson award. Canadian Journal of Botany [Cover image] 85: 533-37 .
  
• Tran HT, Ferrar, T, Ulke A and Moorhead, GBG (2007) Purification of PP2Ac from bovine heart. Methods in Mol. Biol. Vol 365: 127-32.
• Goodarzi, A., P. Douglas, G.B.G Moorhead, S.P. Lees-Miller (2007) Protein phosphatase inhibitors define PP2A as a regulator of ataxia-telangiectasia mutated (ATM). Methods in Mol. Biol. Vol 365: 47-60.
• Moorhead, G.B.G., TA. Haystead and C. MacKintosh (2007) Synthesis and use of microcystin- and microcystin-biotin-Sepharose for the purification of PPP family protein phosphatases. Methods in Mol. Biol. Vol 365: 39-46.
• Yan M Chen, Tony Ferrar, Elke Lohmeir-Vogel, Nick Morrice, Yutaka Muzino, Byron Berenger, Ken K Ng, Doug G Muench and Greg B. G. Moorhead (2006) The PII signal transduction protein of Arabidopsis thaliana forms a metabolite regulated complex with plastid N-acetyl glutamate kinase. J. Biol. Chem. 281: 5726-5733.
• Laura Trinkle-Mulcahy, Jens Andersen, Yun Wah Lam, Greg Moorhead, Matthias Mann and Angus I. Lamond (2006) RePO-MAn is a cell cycle-regulated PP1 targeting subunit that recruits PP1g to anaphase chromatin. J. Cell Biol 172: 679-92. Faculty of 1000 Biology: evaluations for Trinkle-Mulcahy L et al J Cell Biol 2006 Feb 27 172 (5) :679-92 http://www.f1000biology.com/article/id/1066927/evaluation.
• Kerk, D., T.R. Conley, F.A. Rodriguez, D.W. Smith, M. Gribskov, H.T. Tran, Mhairi Nimick, Douglas Muench and G.B.G. Moorhead. (2006) A dual-specificity protein phosphatase in Arabidopsis contains a phylogenetically dispersed and ancient carbohydrate-binding domain, which binds the polysaccharide starch. Plant J. 46: 400-13.
• Templeton, G. and G.B.G. Moorhead (2005) The phosphoinositide 3-kinase related kinases (PIKKs) of Arabidopsis thaliana. EMBO Rep. 6: 723–728.