Adaptation of sensory neurons to hyalectin and decorin proteoglycans

J Neurosci. 2005 May 18;25(20):4964-73. doi: 10.1523/JNEUROSCI.0773-05.2005.

Abstract

Proteoglycans are abundantly expressed in the pathways of developing and regenerating neurons, yet the responses of neurons to specific proteoglycans are not well characterized. We have shown previously that one chondroitin sulfate proteoglycan (CSPG), aggrecan, is potently inhibitory to sensory axon extension in short-term assays and that over time, embryonic neurons adapt to aggrecan-mediated inhibition through the transcriptional upregulation of integrin expression (Condic et al., 1999). Here, we have compared the response of embryonic sensory neurons to structurally distinct CSPGs that belong to either the hyalectin (or lectican) family of large, aggregating proteoglycans or the decorin (or small leucine-rich proteoglycan) family of smaller proteoglycans. Both of these structurally diverse proteoglycan families are expressed in developing embryos and inhibit outgrowth of embryonic sensory neurons in short-term cultures. These results document a previously uncharacterized inhibitory function for the decorin-family proteoglycan biglycan. Interestingly, embryonic neurons adapt to these diverse proteoglycans over time. Adaptation is associated with upregulation of select integrin alpha subunits in a proteoglycan-specific manner. Overexpression of specific integrin alpha subunits improves neuronal regeneration on some but not all decorin-family CSPGs, suggesting that neurons adapt to inhibition mediated by closely related proteoglycans using distinct mechanisms. Our findings indicate that CSPGs with diverse core proteins and distinct numbers of chondroitin sulfate substitution sites mediate a similar response in sensory neurons, suggesting that increased integrin expression may be an effective means of promoting axonal regeneration in the presence of diverse inhibitory proteoglycan species in vivo.

Publication types

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

MeSH terms

  • Adaptation, Physiological / drug effects*
  • Adaptation, Physiological / physiology
  • Age Factors
  • Animals
  • Axons / metabolism
  • Blotting, Northern / methods
  • Cell Adhesion / drug effects
  • Cells, Cultured
  • Chick Embryo
  • Decorin
  • Dose-Response Relationship, Drug
  • Drug Interactions
  • Extracellular Matrix Proteins / metabolism
  • Extracellular Matrix Proteins / pharmacology*
  • Ganglia, Spinal / cytology
  • Gene Expression Regulation, Developmental / genetics
  • Gene Expression Regulation, Developmental / physiology
  • Hyaluronic Acid / metabolism
  • Hyaluronic Acid / pharmacology*
  • Immunohistochemistry / methods
  • Laminin / pharmacology
  • Nervous System / embryology
  • Nervous System / metabolism
  • Neurofilament Proteins / metabolism
  • Neurons, Afferent / cytology
  • Neurons, Afferent / drug effects*
  • Neurons, Afferent / physiology
  • Notochord / metabolism
  • Proteoglycans / classification
  • Proteoglycans / genetics
  • Proteoglycans / metabolism
  • Proteoglycans / pharmacology*
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Time Factors

Substances

  • Decorin
  • Extracellular Matrix Proteins
  • Laminin
  • Neurofilament Proteins
  • Proteoglycans
  • RNA, Messenger
  • Hyaluronic Acid