Fig. 6

Models of stable information storage by a molecular switch. a PKM-zeta model. Black arrow is protein synthesis of PKM-zeta that occurs during late phase of LTP. It is postulated that singly phosphorylated kinase (Kp) can be autophosphorylated to produce doubly phosphorylated kinase (Kpp), which then stimulates further synthesis of PKM-zeta and stable information storage. How synapse specificity is achieved is not specified. The possibility that atypical PKCs undergo such regulated phosphorylation has not been confirmed in recent work [62]. From [55]. b CaMKII model. LTP induction leads to autophosphorylation of CaMKII T286, which leads to persistent activation of the kinase and binding to the NMDA channel within the potentiated spine, thereby establishing synapse-specificity. If a subunit gets dephosphorylated (upward red arrow), the subunit is rephosphorylated by a neighboring active subunit. Protein turnover (downward black arrow) occurs by subunit exchange. A newly inserted unphosphorylated subunit will be phosphorylated by a neighboring subunit. Thus the switch will be stable despite phosphatase activity and protein turnover. From [60]