Cholesterol 3-sulfate interferes with cornified envelope assembly by diverting transglutaminase 1 activity from the formation of cross-links and esters to the hydrolysis of glutamine.
The loss of transglutaminase 1 enzyme (TGase 1) activity causes lamellar ichthyosis. Recessive X-linked ichthyosis (XI) results from accumulation of excess cholesterol 3-sulfate (CSO(4)) in the epidermis but the pathomechanism how elevated epidermal CSO(4) causes ichthyosis is largely unknown. Here we provide evidence that XI is also a consequence of TGase 1 dysfunction. TGase 1 is a key component of barrier formation in keratinocytes: it participates in the cross-linking of cell envelope (CE) structural proteins, and also forms the lipid bound envelope by esterification of long chain omega-hydroxyceramides onto CE proteins. Using involucrin and an epidermal omega-hydroxyceramide analog as substrates, kinetic analyses revealed that at membrane concentrations above 4 mol %, CSO(4) caused a marked and dose-dependent inhibitory effect on isopeptide and ester bond formation. Sequencing of tryptic peptides from TGase 1-reacted involucrin showed a large increase in deamidation of substrate glutamines. We hypothesize that supraphysiological levels of CSO(4) in keratinocyte membranes distort the structure of TGase 1 and facilitate the access of water into its active site causing hydrolysis of substrate glutamine residues. Our findings provide further evidence for the pivotal role of the TGase 1 enzyme in CE formation.
Nemes
Z
Z
Laboratory of Skin Biology, NIAMSD, National Institutes of Health, Bethesda, Maryland 20892-2752, USA.
Demény
M
M
Marekov
L N
LN
Fésüs
L
L
Steinert
P M
PM
D001483:Base Sequence; D002788:Cholesterol Esters / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers; D004817:Epidermis / Q000201:enzymology / Q000378:metabolism*; D004951:Esterification; D005998:Glycine / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D008239:Lysine / Q000737:chemistry; D009154:Mutation; D011498:Protein Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011503:Transglutaminases / Q000378:metabolism*
D002788:Cholesterol Esters; D017931:DNA Primers; D011498:Protein Precursors; D011994:Recombinant Proteins; C032253:involucrin; D011503:Transglutaminases; C105804:transglutaminase 1; D008239:Lysine; C007045:cholesteryl sulfate; D005998:Glycine