The role of heparan sulfate proteoglycans in the regulation of hedgehog/Sonic hedgehog morphogen function in vivo and in vitro

PD Dr. Kay Grobe

Successful applicants will aim at the detailed molecular analysis of Drosophila Hedgehog (Hh) and vertebrate Sonic hedgehog (Shh)/heparan sulfate (HS) interactions. This will include the isolation and characterization of defined HS glycosaminoglycan chains from cell lines transfected with various combinations of HS biosynthetic enzymes, and analysis of the specific binding motifs present on the HS chain using mass spectrometry (Mormann). HS chains isolated from wild type and mutant mouse tissues deficient in HS synthesizing enzymes or deficient in specific proteoglycans will be spotted on glass chips to determine HS sulfation requirements for Hh/Shh binding (Musti, Grobe). The extensive HS library already established in the Grobe lab will further be used for functional in vitro assays, such as modulation of Shh release from producing cells, Shh stabilization in the extracellular environment, and metalloprotease activation. In combination with an extensive cDNA collection for the expression of HS-binding deficient Hh and Shh mutants, the requirements for functionally relevant carbohydrate/protein interactions can be determined on a molecular level.
Most recently, we became interested in HS-dependent regulation of cell surface sheddases, such as the ADAM (A disintegrin and metalloprotease) family members 10, 12 and 17. We also found novel regulators of Shh release from producing cells that require further characterization. This will lead to a better understanding of the regulation of HS-dependent morphogen functions in development and disease.

Suggested doctoral research projects (you are welcome to suggest your own!)

  1. Molecular characterization of the Heparan Sulfate (HS) motif required for the specific binding and modulation of biological function of the morphogen Sonic hedgehog (Shh) (Grobe, Rajan, Peter-Katalinić)
  2. Characterization of three-dimensional conformational changes of Sonic hedgehog (Shh) following HS binding of the morphogen, and their biological function (Grobe, Mandar, Musti, Seidler, Rajan)

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