Thymosin α1 Interacts with Hyaluronic Acid Electrostatically by Its Terminal Sequence LKEKK

Abstract

Thymosin α1 (Tα1), is a peptidic hormone, whose immune regulatory properties have been demonstrated both in vitro and in vivo and approved in different countries for treatment of several viral infections and cancers. Tα1 assumes a conformation in negative membranes upon insertion into the phosphatidylserine exposure as found in several pathologies and in apoptosis. These findings are in agreement with the pleiotropy of Tα1, which targets both normal and tumor cells, interacting with multiple cellular components, and have generated renewed interest in the topic. Hyaluronan (HA) occurs ubiquitously in the extracellular matrix and on cell surfaces and has been related to a variety of diseases, and developmental and physiological processes. Proteins binding HA, among them CD44 and the Receptor for HA-mediated motility (RHAMM) receptors, mediate its biological effects. NMR spectroscopy indicated preliminarily that an interaction of Tα1 with HA occurs specifically around lysine residues of the sequence LKEKK of Tα1 and is suggestive of a possible interference of Tα1 in the binding of HA with CD44 and RHAMM. Further studies are needed to deepen these observations because Tα1 is known to potentiate the T-cell immunity and anti-tumor effect. The binding inhibitory activity of Tα1 on HA-CD44 or HA-RHAMM interactions can suppress both T-cell reactivity and tumor progression.

NMR Characterization of the Interactions Between Glycosaminoglycans and Proteins

“…Studies have shown that the second binding site plays a major role in binding. Studies on Tα1 indicated that the binding is mainly related to its terminal L 16 KEKK 20 ( Mandaliti et al, 2017 ). The combination of HA and these two substances occurred mainly through electrostatic forces, which was different from the role of HA with TSG-6 and CD44.…”

Thymosin Alpha1-Fc Modulates the Immune System and Down-regulates the Progression of Melanoma and Breast Cancer with a Prolonged Half-life

“…Tα1 was also recently proven to interact with hyaluronic acid (HA) by its C-terminal sequence LKEKK 28 . Tα1 shares the similar sequences with CD44 and RHAMM which both can bind with HA.…”

Glycosaminoglycan-Protein Interactions by Nuclear Magnetic Resonance (NMR) Spectroscopy

“…Although use of waterLOGSY in studies of protein-glycan interactions is common, an example involving GAG has been published only recently. Interestingly, in that study, Mandaliti et al did not use the experiment to probe the ligand, but to identify protein residues that are involved in hyaluronan binding [ 33 ], providing a good demonstration of the versatility of the experiment. Although information from waterLOGSY is limited to hydration, it can often be used to create more accurate models and provide a deeper understanding of the energetics of binding.…”