Khaled A. Machaca
Associate Professor
Ph.D., Emory University
Office: (501) 603-1596
Lab: (501) 603-1597
Email: kamachaca@uams.edu

We are interested in the regulation and specificity of calcium (Ca²⁺) signaling pathways. Ca²⁺ is an important second messenger for various cellular functions ranging from secretion to fertilization. Ca²⁺ signaling is mediated through a rise in cytoplasmic Ca²⁺, either by Ca²⁺ release from intracellular stores, or Ca²⁺ influx from the extracellular space. We are investigating the modulation of Ca²⁺ signaling during the cell cycle in Xenopus oocytes.  These studies use confocal Ca²⁺ imaging, immunolocalization, kinase assays, and various other biochemical and molecular approaches.

We are also interested in the role of Ca²⁺ signaling in the progression of the meiotic cell cycle.  We have recently shown that cytoplasmic Ca²⁺ negatively regulates entry into meiosis and is required for the completion of meiosis I.  We are presently investigating the signal transduction cascade involved in this regulation, using biochemical and molecular approaches.  

Another interest in the Lab is the regulation and function of the transient receptor (TRP) channel family.  We have recently cloned the Xenopus homologue of trpv6 and are investigating its biophysical properties and function in the oocyte.  These studies rely primarily on electrophysiological approaches to understand the regulation of this channel.

 As a collaboration with the Chow Lab at UAMS we are studying the role of RNAi as an antiviral immune defense mechanism in the worm C. elegans.  These studies employ molecular, biochemical, genetic and virology techniques.  

Dr. Machaca's Laboratory Homepage

Representative Publications (5)

Wilkins, C., Dishong, R., Moore, S.C., Whitt, M.A., Chow, M., Machaca, K. (2005) RNA interference is an antiviral defence mechanism in Caenorhabditis elegans.  Nature,  In Press. 

Machaca, K. (2004)  Increased sensitivity and clustering of elementary Ca²⁺ release events during oocyte maturation.  Developmental Biology  275, 170-182. 

Sun, L. and Machaca, K. (2004)  Ca²⁺_cyt negatively regulates the initiation of oocyte maturation.  Journal of Cell Biology  165, 63-75.

Machaca, K. (2003).  Ca²⁺-calmodulin dependent protein kinase II potentiates store-operated Ca²⁺ current.  Journal of Biological Chemistry  278, 33730-33737.  

Machaca, K. and Haun, S. (2002).  Induction of MPF during Xenopus oocyte maturation uncouples Ca²⁺ store depletion from Store-Operated Ca²⁺ Entry.  Journal of Cell Biology  156, 75-86.

Link to Dr. Machaca at PubMed

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