Faculty Directory
 Carissa M. Krane Associate Professor Office: SC-223C/133
Phone: (937) 229-3427 Fax: (937) 229-2021 Email:Carissa M. Krane Curriculum Vitae |
Research: Molecular Physiology and Functional Genomics Mammalian Fluid Homeostasis: Aquaporins The maintenance of fluid homeostasis is a critical parameter in establishing and maintaining normal lung physiology. Control of membrane water flux through membrane water pores (aquaporins; AQP) is essential for the ability of an organism to adapt to changing fluid environments. We have found that perturbations in fluid handling in the lung can result in an asthma-like bronchoconstrictive response in a mouse model in which AQP5, a molecule important in water flow in the lung, has been disrupted. We do not currently understand how and why disruptions in this water channel result in an asthma-like pathophysiological state in mice. The objectives of our studies are to determine the functional importance of AQP5 in fluid homeostasis in the context of whole animal physiology and pathophysiology using an Aqp5 knockout mouse. Using the tools of molecular biology and physiology, we have begun to address specific questions regarding the physiological role of AQP5 in mouse lung, as well as at the cellular and molecular levels. The major research interests in this arena include:
The insights gained from these studies have the potential to aid in the development of novel genetic and therapeutic resources for preventing and/or treating conditions of fluid dysregulation. For more information, see a current review on aquaporins. Cryopreservation: Cold acclimation and Freeze Tolerance in Cope’s Gray Treefrog, Hyla chrysoscelis Some organisms inhabiting regions with sub-freezing temperatures are intolerant of freezing and avoid ice formation by mechanisms such as supercooling. Others, like Cope’s gray treefrog H. chrysoscelis, tolerate actual freezing and implement mechanisms that minimize damage from the formation of ice crystals. Among these are the accumulation of solutes that may serve a variety of functions, including cryoprotection (stabilization of protein and/or membrane structure and function) and osmotic agent (regulating the distribution of water between intracellular and extracellular fluids). Upon freezing, a number of amphibian species liberate glucose to accomplish these physiological objectives. However, frogs of the gray treefrog complex – H. chrysoscelis and its tetraploid sister species H. versicolor – are unusual in that they also accumulate glycerol during cold acclimation before freezing. It is likely that this glycerol is synthesized by the liver and is eventually released to the circulation and distributed to tissues throughout the body. Glycerol may circulate at elevated concentration (and accumulate at high concentrations in tissues) in cold-acclimated organisms for weeks or months, as long as the animals remain cold. Although the function of this glycerol has not been definitively established—and other frogs that tolerate freezing do so without glycerol—the presumption is that this solute acts as a cryoprotectant as described above. Thus, it is likely that glycerol transport across cell membranes—whether to exit hepatocytes, to enter other cells as a protective solute, or to be reabsorbed following glomerular filtration—is an important physiological demand during cold acclimation in this group of frogs. At the same time, pathways for water flux must be maintained, both for water balance during cold acclimation (e.g. renal water reabsorption, or potentially water redistribution) and for the eventuality of freezing (when water is likely distributed between fluid compartments, and which may well occur too quickly for upregulation of water transport pathways). Both glycerol and water transport can be accomplished via proteins from the MIP family. Some of these proteins (aquaporins, AQP) function as selective water channels, whereas others (glyceroporins, GLP) additionally transport small organic solutes like glycerol. We hypothesize that tissues from gray treefrogs would express AQPs and GLPs, and that the pattern of their expression among tissues would relate to roles in water and glycerol transport. To test these hypotheses and predictions we have cloned three novel AQPs. Our current efforts are focused on functionally characterizing these water channels using Xenopus oocyte expression assays. In addition, we are using quantitative real-time PCR and immunohistochemistry to characterize thermal and tissue regulation of the AQPs.
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