Evidence for Increased Proteolysis in Intact β Thalassemia Erythroid Cells

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Abstract
Mxh excess u chain is synthesized, but little accumlates in the erythroid ells of patients with hanozycpus B thalassda. To dew if the proteases Imam to exist in erythmid cells play a role in the destruction or alteration of any of this excess α dmin, thalassemic and nmthalassemic erythroid cells were incubated for 90 minutes with 3H-leucine. The cells wxe then washed, and incubated Wioe for 15 minutes in 100 volunes of add leucine-rich media, a pmcedure which eliminates alrost all intracœllular TCA soluble radioadety. After these incubations levels of TCA soluble and TCA precipitable radioactivity in the cell lysates were detmdmdI and cells incubated for 120 minutes move in tm volumes of Ieucinerich media. At the end of this incubation, total Kl soluble and precipitable radioactivity was again determiraed in the œll lysate, and also in the tm hour incubaticn media. Tb total increase in TCA soluble radioactivity in the ells and their media was divided by the 0 time TCA precipitable radioactivity, to detadne the percmt proteolysis labelled globin chains. In five mtml patients Perœnt proteolysis ranged from 0 to 3.10 (* = 1.50); in four sewre and three mild thalassemia patients percent pmteolysis ranged fran 5.80 to 14.1 (X = 11.0). The difference between the control and thalassemia groups was significant at ap of <0.002. This data is the first direct evidence that more proteolysis takes place in intact thalassemia œlls than in non-thalassemia cells.