Ketohexokinase: Expression and Localization of the Principal Fructose-metabolizing Enzyme

Ketohexokinase (KHK, also known as fructokinase) initiates the pathway through which most dietary fructose is metabolized. Very little is known about the cellular localization of this enzyme. Alternatively spliced KHK-C and KHK-A mRNAs are known, but the existence of the KHK-A protein isoform has not been demonstrated in vivo. Using antibodies to KHK for immunohistochemistry and Western blotting of rodent tissues, including those from mouse knockouts, coupled with RT-PCR assays, we determined the distribution of the splice variants. The highly expressed KHK-C isoform localized to hepatocytes in the liver and to the straight segment of the proximal renal tubule. In both tissues, cytoplasmic and nuclear staining was observed. The KHK-A mRNA isoform was observed exclusively in a range of other tissues, and by Western blotting, the presence of endogenous immunoreactive KHK-A protein was shown for the first time, proving that the KHK-A mRNA is translated into KHK-A protein in vivo, and supporting the suggestion that this evolutionarily conserved isoform is physiologically functional. However, the low levels of KHK-A expression prevented its immunohistochemical localization within these tissues. Our results highlight that the use of in vivo biological controls (tissues from knockout animals) is required to distinguish genuine KHK immunoreactivity from experimental artifact. (J Histochem Cytochem 57:763–774, 2009)     

The Life of Marble: The Experience and Meaning of Work in the Marble Quarries of Carrara

Based on ethnographic research in the marble quarries of Carrara in north Italy, this article offers an experiential interpretation of work and labour. Intended as a critique of more structurally determined accounts of the labour process, the article examines the ways in which the experience and meanings of work can be found in the domain of intersubjectivity, articulated both in the discursive practices and interactions of co-workers, as well as through the everyday embodied activity and lived experience of quarrying itself. The first section deals with the relationship between quarry workers and the natural environment. In the second section I explore the relationship between craft identity, the embodied experience of labour and collective narratives of masculinity.