ISOLATION OF HIGH-AFFINITY MURINE INTERLEUKIN-2 RECEPTORS AS DETERGENT-RESISTANT MEMBRANE COMPLEXES

Murine T cells and T cell lines bearing high‐ and low‐affinity receptors for interleukin (IL) 2 were chemically cross‐linked to radiolabeled IL 2 and subjected to differential detergent extractions to evaluate the extent of IL 2 receptor association with the nonionic detergent‐resistant framework of the plasma membrane. Low‐affinity receptors were readily solubilized by nonionic detergent extraction of whole cross‐linked cells, while solubilization of high‐affinity receptors required a stronger ionic detergent suggesting their association with a membrane structure that is resistant to nonionic detergents. To achieve physical separation of low‐ and high‐affinity receptors, cells cross‐linked to 125I‐labeled IL 2 were centrifuged through a sucrose barrier containing Triton X‐100. Alternatively, Triton X‐114 extracts of plasma membrane fractions were partitioned into aqueous and detergent phases. By either approach, high‐affinity receptors differed from low‐affinity ones by their increased density and consisted of detergent‐resistant complexes containing p55‐p75 heterodimers. The low‐affinity receptors, on the contrary, were of low density and consisted exclusively of detergent‐soluble p55 subunits. High density and resistance to nonionic detergent extraction of high‐affinity IL 2 receptors suggest their integration into lateral microdomains of the detergent‐resistant framework of the plasma membrane. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim