Abstract
Purpose: :
Corneal stroma extracellular matrix (ECM) glycosaminoglycans (GAGs) include keratan sulfate (KS), chondroitin sulfate (CS), and hyaluronic acid (HA). Embryonic corneal keratocytes and sensory nerve fibers grow and differentiate according to chemical cues they receive from their ECM. This study asks what proteins that might regulate keratocytes or corneal nerve growth cone immigration interact with corneal GAGs.
Methods: :
Biotinylated KS, CSA, and HA were prepared, and used in Invitrogen’s v4 microarray to assess their interactions with 8268 proteins and a custom array of 88 extracellular epitopes of nerve growth-related proteins. Surface Plasmon Resonance (SPR) was performed with biotinylated KS and SLIT2, and their Ka, Kd, and KD determined.
Results: :
Highly sulfated KS interacted with 217 v4 proteins, including 75 kinases, several membrane or secreted proteins, many cytoskeletal proteins, and many nerve function proteins. CSA interacted with 24 v4 proteins including 10 kinases and 2 cell surface proteins. HA interacted with 6 v4 proteins including several matrix-related structural proteins. Of 85 ECM nerve-related epitopes, KS bound 40 proteins, including SLIT, 2 ROBOs, 9 EPHs, 8 Ephrins (EFNs), 8 semaphorins (SEMAs) and 2 nerve growth factor receptors. CSA bound 9 proteins, including ROBO 2, 2 EPHs, 1 EFN, 2 SEMAs, and NETRIN4. HA bound no extracellular nerve-related epitopes. SPR confirmed that KS binds SLIT2 strongly. KS core protein mimecan/osteoglycin bound 15 v4 proteins.
Conclusions: :
These observations suggest that stromal GAGs bind and could alter the availability or conformation of many proteins that may influence keratocyte and nerve growth in the cornea.
Keywords: proteoglycans/glycosaminoglycans • proteomics • cornea: stroma and keratocytes