A Model System for Studying the Effects of Hormones on Lysosomal Polyphosphoinositide Metabolism
Lysosomes, whose functions involve receptor mediated endocytosis, phagosome-lysosome fusion, exocytosis and autophagy, are generally believed to be under the influence of various extracellular stimuli. Rapid morphological changes of lysosomes are observed in response to these stimuli suggesting that a mechanism exists to signal primary lysosomes to participate in subsequent physiological events. Lysosomes from livers of starved rats (DeDuve, 1969) and those from livers perfused with glucagon or cAMP (Ashford and Porter, 1962; Deter and DeDuve, 1967; Mortimore et al., 1978; Saito and Ogawa, 1974) rapidly undergo remarkable structural transformations associated with autophagy. The stimulation of lysosomal membrane rupture under standard homogenization procedures is attributed to increased volume of the resulting autophagolysosomes. In our laboratory (Schroeder et al., 1974), it was observed that liver lysosomes from normal chickens exhibited a significant diurnal variation in fragility, suggesting dietary and hormonal influences on this process. We became interested in the possibility that lysosomal membrane protein phosphorylation/dephosphorylation reactions may be under hormonal regulation and might result in altered membrane function.
KeywordsHigh Performance Liquid Chromatography Phosphatidylinositol Kinase Ammonium Formate Lysosomal Membrane Lysosomal Fraction
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