Regulation of enterocyte apoptosis by acyl-CoA synthetase 5 splicing.
OBJECTIVE
The constant renewal of enterocytes along the crypt-villus axis (CVA) of human small intestine is due to cell-inherent changes resulting in the apoptotic cell death of senescent enterocytes. The aim of the present study was to examine underlying molecular mechanisms of the cell death at the villus tip.


METHODS
Characterization of human acyl-coenzyme A (CoA) synthetase 5 (ACSL5) was performed by cloning, recombinant protein expression, biochemical approaches, and several functional and in situ analyses.


RESULTS
Our data show that different amounts of acyl-CoA synthetase 5-full length (ACSL5-fl) and a so far unknown splice variant lacking exon 20 (ACSL5-Delta 20) are found in human enterocytes. In contrast with the splice variant ACSL5-Delta 20, recombinant and purified ACSL5-fl protein is active at a highly alkaline pH. Over expression of ACSL5-fl protein is associated with a decrease of the anti-apoptotic FLIP protein in a ceramide-dependent manner and an increased cell-surface expression of the death receptor TRAIL-R1. Expression analyses revealed that the ACSL5-fl/ACSL5-Delta 20 ratio increases along the CVA, thereby sensitizing ACSL5-fl-dominated cells at the villus tip to the death ligand TRAIL, which is corroborated by functional studies with human small intestinal mucosal samples and an immortalized human small intestinal cell line.


CONCLUSIONS
Our results suggest an ACSL5-dependent regulatory mechanism that contributes to the cellular renewal along the CVA in human small intestine. Deregulation of the ACSL5-fl/ACSL5-Delta 20 homeostasis in the maturation and shedding of cells along the CVA might also be of relevance for the development of intestinal neoplasia.
Institute of Pathology, Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University, Aachen, Germany. ngassler@ukaachen.de
Nikolaus
N
Gassler
Wilfried
W
Roth
Benjamin
B
Funke
Armin
A
Schneider
Frank
F
Herzog
Jens J W
JJ
Tischendorf
Kerstin
K
Grund
Roland
R
Penzel
Ignacio G
IG
Bravo
John
J
Mariadason
Volker
V
Ehemann
Jaromir
J
Sykora
Tobias L
TL
Haas
Henning
H
Walczak
Tom
T
Ganten
Hanswalter
H
Zentgraf
Peter
P
Erb
Angel
A
Alonso
Frank
F
Autschbach
Peter
P
Schirmacher
Ruth
R
Knüchel
Jürgen
J
Kopitz
D000368:Aged; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D018938:Caco-2 Cells; D053148:Caspase 3 / Q000378:metabolism; D002446:Celiac Disease / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D002518:Ceramides / Q000096:biosynthesis; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D004386:Duodenum / Q000201:enzymology* / Q000473:pathology; D004721:Endoplasmic Reticulum / Q000201:enzymology; D020895:Enterocytes / Q000201:enzymology* / Q000473:pathology; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000201:enzymology* / Q000473:pathology; D008871:Microvilli / Q000201:enzymology / Q000473:pathology; D008875:Middle Aged; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D014162:Transfection
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002518:Ceramides; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C105190:TNFRSF10A protein, human; D053148:Caspase 3; D003066:Coenzyme A Ligases; C485465:ACSL5 protein, human