title: Inhibitory role of TACE/ADAM17 cytotail in protein ectodomain shedding.
abstract: OBJECTIVE
  To determine if the cytotail of the principal sheddase tumor necrosis factor-α converting enzyme (TACE; ADAM17) controls protein ectodomain shedding.
  
  
  METHODS
  Site-directed mutagenesis was performed to derive TACE variants. The resulting TACE expression plasmids with amino acid substitutions in the extracellular, cysteine-rich disintegrin domain (CRD) and/or deleted cytotail, along with an expression vector for the enhanced green fluorescence protein were transfected into shedding-defective M1 mutants stably expressing transmembrane L-selectin or transforming growth factor (TGF)-α. The expression levels of the TACE substrates at the cell surface were determined by flow cytometry.
  
  
  RESULTS
  Consistent with published data, a single point mutation (C600Y) in the CRD led to shedding deficiency. However, removal of the cytotail from the C600Y TACE variant partially restored ectodomain cleavage of TGF-α and L-selectin. Cytotail-deleted mutants with any other substituting amino acid residues in place of Cys600 displayed similar function compared with tail-less C600Y TACE.
  
  
  CONCLUSIONS
  The cytotail plays an inhibitory role, which becomes evident when it is removed from an enzyme with another mutation that affects the enzyme function.
authors: Xiaojin Li, Liliana Pérez, Huizhou Fan, Department of Physiology and Biophysics, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, United States.
authors: Xiaojin
authors: X
authors: Li
authors: Liliana
authors: L
authors: Pérez
authors: Huizhou
authors: H
authors: Fan