A number of organelles contained within mammalian cells have been implicated in the selective sequestration of chemical entities including drug molecules. Specifically, weakly basic molecules have been shown to selectively associate with either the mitochondrial compartment or lysosomes; however, the structural basis for this differentiation has not been understood. To investigate this, we have identified a series of seven weakly basic compounds, all with pK a near neutrality, which have different sequestration sites within the multidrug-resistant HL-60 human leukemic cell line. Three of the compounds were selectively sequestered into the mitochondria of the cells, whereas the remainder were predominantly localized within lysosomes. Using specific chemical inhibitors to disrupt either mitochondrial or lysosomal accumulation capacity, we demonstrated that accumulation of these compounds into respective organelles are not competitive processes. Comparison of the permeability characteristics of these compounds as a function of pH revealed striking differences that correlate with the intracellular sequestration site. Only those compounds with significantly reduced permeability in the ionized state relative to the un-ionized state had the capacity to accumulate within lysosomes. Alternatively, those compounds with relatively pH-insensitive permeability selectively accumulated into mitochondria. Using novel quantitative assays for assaying drug accumulation into subcellular organelles, we demonstrated a correlation between these permeability characteristics and the lysosomal versus mitochondrial accumulation capacity of these compounds. Together, these results suggest that the selective accumulations of weakly basic compounds in either lysosomes and mitochondria occur via exclusive pathways governed by a unique permeability parameter.
us-map.html ¶ A list of severe manifestations of monkeypox can be found at https://emergency. cdc.gov/han/2022/han00475.asp. ** During the study period and as of October 21, 2022, CDC was notified by state and local jurisdictions of five decedents whose death certificates included monkeypox as a cause of death or contributing factor, six decedents whose cause of death is still under active investigation, and one decedent in whom the death was not monkeypox-related. Additional monkeypox cases involving severe disease or death might not be included in this report if CDC has not yet been notified about the case or if the case occurred outside of the study period.
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