Understanding the Interaction Between Itch and TAX1BP1: What Does Zinc Have to Do With It?



Students: Joel Brandis, Ashley Cowen

Faculty Adviser: Barbara T. Amann (Dept. of Chemistry)

Abstract

Zinc deficiency is a major public health problem and leads to a suppressed immune system. A major inflammation pathway that is responsible for regulating inflammation is the Nuclear Factor Kappa B (NF-kB) signaling pathway. Many key proteins in this pathway bind to zinc and potentially explain the response of the immune system to zinc deficiency. Negative regulation of this pathway is mediated by the A20 complex, which is composed of four proteins including Tax 1-binding protein 1 (TAX1BP1) and Itch. The TAX1BP1 and Itch proteins interact with one another through two PPXY zinc finger domains and four WW domains, respectively. We have synthesized single peptides corresponding to each of these domains and have found the tightest interaction occurs between of the first Itch WW domain (WW1) and the second TAX1BP1 zinc finger (TAXF2) when zinc is present compared to any of the other Itch WW domains that bind the TAX1BP1 zinc fingers better in the absence of zinc. Through mutational studies, we have determined that four amino acids residues located in the WW1 but not in WW2 are responsible for this switch of preference for zinc bound versus apo-TAX1BP1 zinc fingers.