T-cell immunoglobulin and mucin domain 2 (TIM-2) is a target of ADAM10-mediated ectodomain shedding

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Abstract

T-cell immunoglobulin and mucin domain (TIM)-2 is expressed on activated B cells. Here, we provide evidence that murine TIM-2 is a target of ADAM10-mediated ectodomain shedding, resulting in the generation of a soluble form of TIM-2. We identified ADAM10 but not ADAM17 as the major sheddase of TIM-2, as shown by pharmacological ADAM10 inhibition and with ADAM10-deficient and ADAM17-deficient murine embryonic fibroblasts. Ionomycin-induced or 2′(3′)-O-(4-benzoylbenzoyl) ATP triethylammonium salt-induced shedding of TIM-2 was abrogated by deletion of 10 juxtamembrane amino acids from the stalk region but not by deletion of two further N-terminally located blocks of 10 amino acids, indicating a membrane-proximal cleavage site. TIM-2 lacking the intracellular domain was cleaved after ionomycin or 2′ (3′)-O-(4-benzoylbenzoyl) ATP triethylammonium salt treatment, indicating that this domain was not involved in the regulation of ectodomain shedding. Moreover, TIM-2 shedding was negatively controlled by calmodulin. Shed and soluble TIM-2 interacted with H-ferritin. In summary, we describe TIM-2 as a novel target for ADAM10-mediated ectodomain shedding, and reveal the involvement of ADAM proteases in cellular iron homeostasis.

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