Sulfated glycoprotein-2 is increased in rat hippocampus following entorhinal cortex lesioning

Thios study showed responses of sulfated glycoprotein-2 (SGP-2) in the rat hippocampus after deafferenting lesion. SGP-2 is a plasma protein that also occurs in many peripheral tissues. In some circumstances, elevations of SGP-2 mRNA are associated with cell degeneration and responses to injury. This study used entorhinal cortex lesions (ECL) to partially deafferent the hippocampus by damaging the perforant path and to induce synaptic remodeling. SGP-2 mRNA is increased in hippocampal astrocytes after ECL. Western blot analysis of soluble hippocampal proteins identified 3 major forms of rat SGP-2 protein: a precursor (61 kDa) and 2 reduced subunits at 39.5 and 35 kDa. These forms increased at 4 days post ECL ipsilaterally to the lesion. By immunocytochemistry (ICC), SGP-2 showed an increased immunoreactivity on the lesioned side by 2 days post ECL that continued through 14 days post ECL. Besides immunopositive astrocytes, punctate immunochemical reaction products occurred among the degenerating fibers of the perforant path. We conclude that changes of SGP-2 protein in the hippocampus after ECL occur roughly in parallel with increases of SGP-2 mRNA. The punctate immuno-deposits could represent secreted SGP-2 and may be useful as a marker for degenerating pathways.