The liberation of CD44 intracellular domain modulates adenoviral vector transgene expression

J Biol Chem. 2012 Sep 21;287(39):32697-707. doi: 10.1074/jbc.M112.347369. Epub 2012 Aug 3.


The success of gene therapy in the ocular environment is partly due to the presence of hyaluronan in vitreous. Here we explore the mechanism of hyaluronan-mediated enhancement of adenoviral vector transgene expression. Introduction of hyaluronan receptor CD44 into CD44-negative cells followed by transduction in the presence of vitreous with an adenoviral vector containing an IL-12-coding transgene increases IL-12 secretion. We demonstrate that sequential CD44 proteolysis is responsible for hyaluronan-mediated enhancement. Metalloproteinase or γ-secretase inhibitors decrease adenoviral-mediated transgene expression. Deletion of these proteolytic sites in CD44 also inhibits transgene expression. Expression of CD44 with a mutation to prevent phosphorylation of serine 325 inhibits the response to vitreous. Expression of the CD44 intracellular domain enhances transgene expression in the absence of vitreous. CD44-mediated enhancement of gene expression was observed with vectors using different promoters and appears because of an increase in mRNA production, not because of an increase in vector transduction as determined by quantitative RT-PCR and quantitative PCR, respectively. These data fit a model where the interaction of hyaluronan in vitreous and CD44 modulates transgene expression by initiating CD44 proteolysis and release of the cytoplasmic domain, resulting in increased transgene transcription.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae*
  • Amyloid Precursor Protein Secretases / antagonists & inhibitors
  • Amyloid Precursor Protein Secretases / genetics
  • Amyloid Precursor Protein Secretases / metabolism
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Enzyme Inhibitors / pharmacology
  • Gene Expression*
  • Genetic Vectors*
  • Humans
  • Hyaluronan Receptors / genetics
  • Hyaluronan Receptors / metabolism*
  • Hyaluronic Acid / genetics
  • Hyaluronic Acid / metabolism
  • Interleukin-12 / biosynthesis
  • Interleukin-12 / genetics
  • Mutation
  • Promoter Regions, Genetic
  • Protein Structure, Tertiary
  • Proteolysis*
  • Transcription, Genetic
  • Transgenes*


  • CD44 protein, human
  • Enzyme Inhibitors
  • Hyaluronan Receptors
  • Interleukin-12
  • Hyaluronic Acid
  • Amyloid Precursor Protein Secretases