Loss-of-Function in SMAD4 Might Not Be Critical for Human Natural Killer Cell Responsiveness to TGF- β

This study was carried out in accordance with approval of the Melbourne Health and Walter and Eliza Hall Institute of Medical Research's Human Research Ethics Committee (approval number: 2013.081). All subjects gave written informed consent for participation and publication. Results and Discussion TGF-β signaling in NK cells is associated with: phosphorylation in SMAD2 and 3, inhibition of IL-15-induced metabolism/proliferation, simultaneous downregulation of CD44, CD49e, and Eomes, and upregulation of CD16 and CD49a expression (7, 10). SMAD family member 4 (SMAD4) belongs to the SMAD family of transcription factor proteins which combine in heterocomplexes with SMAD2 and 3, and still have an unclear role during the signal transduction (11, 12). In this case report, we obtained samples from patients carrying a loss-of-function mutation in the SMAD4 (p.Ser232GInfs*3) expected to generate a protein without function and prone to be degraded upon expression. We accessed by western blot the SMAD4 protein expression, from fresh isolated NK cell by negative selection, two SMAD4-mutants and 2 health donors, and confirmed a lower expression of SMAD4 in both patient samples (data not shown). SMAD4-mutant and healthy donor NK cell phenotypes were assessed by gating the CD56bright and CD56dim subsets from the viable CD3neg, CD14neg, CD20neg, CD45+, CD66bneg, NKp46+ PBMC population. Although all donors were clinically classified as infection-free at time of donati...
Source: Frontiers in Immunology - Category: Allergy & Immunology Source Type: research