Role of Protein Synthesis in Engram Consolidation
It has been established that any learning process is accompanied by the production of specific polypeptides and distinct brain-specific proteins. These protein synthesis processes are completely ineffective immediately after information acquisition, during the active phase of short-term memory. Later on, however, the synthesis of new molecules becomes critical for the formation of long-term memory.
It is precisely through proteins that engram consolidation occurs—the structural and functional stabilization of the memory trace within the nervous system.
Effect of Blockers on Memory Formation
The involvement of proteins in memory mechanisms has been reliably confirmed through experiments utilizing protein synthesis inhibitors (blockers). These substances demonstrated that long-term memory formation is impossible without the generation of new protein molecules.
Key blockers and their effects:
- Puromycin. Its mechanism of action involves the premature release of the nascent protein molecule from ribosomes. When administered to previously trained animals, it shortens retention time. If administered before training, short-term memory remains intact and the acquisition rate of new skills is unchanged, but their consolidation is severely disrupted.
- Cycloheximide (blocks ribosomal translation) and Actinomycin D (blocks transcription). These agents effectively suppress previously acquired skills. If protein synthesis inhibition occurs directly during learning, the acquired skill persists only briefly—from several minutes to one hour.
Key Takeaway: When using inhibitors, profound memory impairments are consistently observed 1–2 hours after administration, corresponding to the timeframe of information transfer into long-term storage.
Brain-Specific Proteins (after H. Hydén)
During learning, as well as accompanying glycolytic reactions in neurons, there is an active accumulation of specific proteins in various brain structures. Several such brain-specific proteins involved in memory processes were isolated by researcher H. Hydén.
- S-100 protein. Considered by researchers to be a glial protein. During learning, it accumulates predominantly in the hippocampus. Its primary function is active interaction with the outer and contractile membranes of neurons. This process proceeds exclusively in the obligatory presence of calcium ions (Ca^{2+}).
- 14-3-2 protein. Chemically, this protein is an enzyme. Unlike S-100, its maximum accumulation occurs in the cerebral cortex.
In addition to these polypeptides, the cholinoceptive protein and the enzyme acetylcholinesterase play important roles in information retention, ensuring the proper function of the synaptic apparatus.