Presence of growth promoting and inhibiting cell adhesion molecules in adult rat sensory neurons after axotomy

GONZALEZ POLO, VIRGINIA; PATTERSON, SEAN I.

Pinamar, Buenos Aires

Congreso; XX Reunión Anual del SAN; 2005

Sociedad Argentina de Neuroquímica

Peripheral nerve axotomy alters protein expression in DRG neurons to promote axon regrowth. In the PNS, this growth is often successful, while it usually fails in the dorsal root entry zone (DREZ), where the axons first encounter the CNS environment. It is known that DREZ astrocytes form at least part of the barrier to regrowth, although the molecules responsible for the inhibition are so far unidentified. METHODS: Unilateral sciatic nerve axotomies were performed on adult rats, and protein expression and distribution were determined by Western blot and immunohistochemistry in the corresponding nerves, ganglia (L4/5) and roots. RESULTS: We found high levels of expression of the Ig-CAM family members thy-1 and L1 in the DRG and central and peripheral processes, both in control and axotomized samples. As both these molecules are known to bind to ?v?3-integrin, we probed for it’s expression in the dorsal roots, and found both subunits to be present regardless of axotomy. Several signal transduction proteins implicated in axon growth (GAP-43, src-kinases) were induced and transported centrally and peripherally, while others (caveolin, cdc42) were not induced. CONCLUSIONS: Neuronal thy-1 is postulated to inhibit axon growth. We show that it is present in centrally-projecting axons of DRG neurons and that it’s cognate receptor is present in the dorsal roots where regeneration fails. We suggest that this interaction may underlie axonal inhbition in the DREZ.