Identification of Transglutaminase-reactive Residues in S100A11

Abstract

The recent finding that S100A11 is a component of the keratinocyte cornified envelope (CE) (Robinson, N. A., Lapic, S., Welter, J. F., and Eckert, R. L. (1997) J. Biol. Chem. 272, 12035-12046) suggests that S100A11 is a transglutaminase (TG) substrate. In the present study we show that S100A11 forms multimers when cultured keratinocytes are challenged by increased levels of intracellular calcium and that multimer formation is inhibited by the TG inhibitor, cystamine. These S100A11 multimers appear to be incorporated into the CE, as immunoreactive S100A11 is detected in purified envelopes prepared from cultured cells and from foreskin epidermis. To study S100A11 as a transglutaminase substrate, recombinant human S100A11 (rhS100A11) was used in a cell-free cross-linking system.

Metastasis-associated S100A4 is a specific amine donor and an activity-independent binding partner of transglutaminase-2

“…The determination of the reactive lysine residue in S100A4, by mass spectrometry and by using alanine mutants, revealed that only one lysine, the penultimate Lys100 in S100A4 is involved in the isopeptide bond formation. This lysine is localized in the disordered C-terminal tail of S100A4 that could be easily accessible for the active site of TG2 as also discussed by others [13,29]. Our studies also demonstrate that S100A4 is not cross-linked to itself by TG2 (as it is not a glutaminse donor of TG2), at least under the experimental conditions used here.…”

Bricks and mortar of the epidermal barrier

“…Finally, we have shown that involucrin is covalently bound to ω-h y d r o x y c e r a m i d e s from the exterior surface of the CE, indicating that involucrin must have been deposited in the intimate vicinity of the cell membrane at an early time . A transporting system has been proposed for positioning involucrin to the cell membrane (Robinson and Eckert, 1998). This model hypothesizes cross-linking of CE building blocks first to S100 proteins, which then dock to annexins to attach to the inner memb-rane surface in a calcium and phospholipid dependent manner.…”

“…As annexins I and II were shown to associate with S100 proteins on calcium binding (Mailliard et al ., 1996;Seemann et al . , 1996), this mechanism may play a role in docking certain early CE protein components to the plasma membrane (Robinson and Eckert, 1998).…”

Specific Citrullination Causes Assembly of a Globular S100A3 Homotetramer

“…Although this biochemical process is believed to be precisely regulated by the intracellular Ca 2ϩ concentration, there remains controversy regarding the mechanism by which PAD and transglutaminase could be activated in vivo, since both require a nearly millimolar level of Ca 2ϩ to exhibit their full activities in vitro (12,18). Several epithelial protein barrier components containing Ca 2ϩ -binding domains have been reported to be natural substrates of PAD (the mature filaggrin subunit, proteolytically processed from profilaggrin (13)) or of transgutaminase (S100A7, S100A10, and S100A11 (14,15)) in skin epidermis or of both these enzymes (trichohyalin (16,17)) in hair follicles. It has been proposed that the Ca 2ϩ ions bound to these proteins are presented to the Ca 2ϩ -dependent proteinmodifying enzymes (8,11); however, more direct evidence is necessary to support this notion.…”