HMGB1 and infection: Moreover, we found instances of pathways that were less activated in APEC O2-GFPpos cells relative to controls than observed during APEC O1-GFP infection, including “Neuregulin signaling and ErbB,” “NF-κB signaling,” and “HMGB1 and ILK signaling.” Neuregulins (NRGs) are a family of structurally related signaling proteins that bind to receptor tyrosine kinases of the ErbB family and mediate a myriad of cellular functions including survival, proliferation, and differentiation in both neuronal and non-neural cells including macrophages.