A role for MAP kinase in regulating ectodomain shedding of APLP2 in corneal epithelial cells.
We previously reported an increased secretion of amyloid precursor-like protein 2 (APLP2) in the healing corneal epithelium. The present study sought to investigate signal transduction pathways involved in APLP2 shedding in vitro. APLP2 was constitutively shed and released into culture medium in SV40-immortalized human corneal epithelial cells as assessed by Western blotting, flow cytometry, and indirect immunofluorescence. Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) caused significant increases in APLP2 shedding. This was inhibited by staurosporine and a PKC-epsilon-specific, N-myristoylated peptide inhibitor. Epidermal growth factor (EGF) also induced APLP2 accumulation in culture medium. Basal APLP2 shedding as well as that induced by PMA and EGF was blocked by a mitogen-activated protein kinase (MAPK) kinase inhibitor, U-0126. Our results suggest that MAPK activity accounts for basal as well as PKC- and EGF-induced APLP2 shedding. In addition, PKC-epsilon may be involved in the induction of APLP2 shedding in corneal epithelial cells.
Xu
K P
KP
Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA.
Zoukhri
D
D
Zieske
J D
JD
Dartt
D A
DA
Sergheraert
C
C
Loing
E
E
Yu
F S
FS
D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D002461:Cell Line, Transformed; D004815:Epidermal Growth Factor / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
C489697:APLP1 protein, human; C084104:APLP2 protein, human; D016564:Amyloid beta-Protein Precursor; D009419:Nerve Tissue Proteins; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate