Cytosolic Events Related to Cell Activation: Potential Interaction between Signal and Energy Transduction Pathways in Smooth Muscle Cells

Abstract

A number of peptide hormones have been shown to induce metabolic and respiratory stimulation in hepatocytes and other mammalian cell types (Balaban and Blum, 1982), demonstrating that there is necessary intercommunication between the signal and energy transduction pathways within the cell. What has not been clear is whether the communication mechanism between these two important pathways is direct or indirect. The answer to this question could have significant impact on our understanding of the regulatory mechanism(s) for cellular energy production. The regulation of cellular energy production has been a major focus of research for many years, with primary candidates for the mechanism(s) of control including the relative levels of various respiratory and phosphorylation substrates (Balaban and Blum, 1982; Rutter and Denton, 1988). Other candidates which have recently gained importance are rate limiting calcium sensitive mitochondrial dehydrogenases (M^cCormack and Denton, 1990). It has also been suggested that calcium dependent changes of mitochondrial volume may play a role in metabolic regulation of hepatocytes (Halestrap, 1989).