From 8cc5ec04ba56803b316e89e60dbdba407b3b1264 Mon Sep 17 00:00:00 2001 From: ocrampal Date: Wed, 29 Apr 2026 11:29:24 +0200 Subject: [PATCH] agiunto ovgcc tun al readme --- neuron/README.md | 21 +++++++++++++++++++++ neuron/presynapse.md | 14 +++++++------- 2 files changed, 28 insertions(+), 7 deletions(-) diff --git a/neuron/README.md b/neuron/README.md index 6891b27..9b43edd 100644 --- a/neuron/README.md +++ b/neuron/README.md @@ -58,6 +58,27 @@ The presynapse does not release blindly. Its behaviour is governed by three inte - The loop closes through Ca²⁺ clearance. If firing is sustained long enough that ATP demand outpaces glucose-driven production, ATP falls, the PMCA and SERCA pumps slow, and residual Ca²⁺ builds between spikes. This elevated residual Ca²⁺ suppresses CDI recovery, causing VGCCs to gradually lock shut and silencing the synapse. Silence stops consuming ATP, allowing the production side to catch up and ATP to recover. The ATP loop therefore has a natural self-resetting property: the same mechanism that causes silence also triggers recovery. - The ATP loop intersects both other loops. It shares Ca²⁺ clearance with the Ca²⁺ loop — pump failure is what connects ATP depletion to VGCC inactivation. It shares the glutamine shuttle with the NT loop — when the astrocyte is energy-starved, conversion efficiency falls and RP replenishment slows, making vesicle depletion more severe and prolonged. ATP depletion is therefore the single point of failure that can cascade across all three loops simultaneously, which is why it is the mechanistic basis of excitotoxic protection. +**VGCC Tuning** In the minutes-to-hours range, the presynapse shifts from "gating" (turning existing channels on/off) to remodeling (changing the physical number of channels). This process is governed by a shift from purely electrical signals to biochemical "state" signals.The primary signal that dictates the density of VGCCs at the terminal is the history of the $Ca^{2+}$ trace, specifically mediated through three core molecular pathways: +1. The RIM-Binding Protein (RBP) Scaffold (Minutes) +The most immediate way to "add" or "eliminate" channels without synthesizing new protein is through lateral mobility. VGCCs aren't bolted down; they are held in place by a scaffold called the Active Zone (AZ), composed of proteins like RIM and Cast. + 1. The Signal: High-frequency activity leads to the phosphorylation of RIM. + 2. The Action: This alters the "slots" available for VGCCs. If RIM is phosphorylated or degraded due to over-activity, it loses its grip on the channel. The VGCC then drifts out of the Active Zone into the "perisynaptic" space. + 3. The Scale: This happens over 5–30 minutes. The channel is still on the membrane, but it's no longer near the vesicles, effectively "eliminating" its influence on neurotransmitter release. +2. Ubiquitin-Mediated Endocytosis (Minutes to Hours) +If the "silence" you described in the ATP loop persists, the cell moves from drifting channels to actually removing them from the surface. + 1. The Signal: Ubiquitin ligases (like Nedd4). These enzymes are often activated by prolonged high internal $Ca^{2+}$ or metabolic stress. + 2. The Action: They tag the VGCC protein with a "trash me" label (ubiquitin). This triggers endocytosis, where the membrane folds inward and swallows the channel, moving it into an internal vesicle for degradation. + 3. The Purpose: This is the ultimate "excitotoxic brake." If the ATP loop can’t recover, the cell physically reduces its capacity for $Ca^{2+}$ entry to prevent permanent damage. +3. Homeostatic Scaling & Gene Expression (Hours to Days)When the "silence" lasts for a long time, the neuron assumes the synapse is underperforming and needs more "ears." + 1. The Signal: Nuclear factor of activated T-cells (NFAT) or CREB. These are transcription factors that reside in the synapse but travel to the nucleus when $Ca^{2+}$ levels stay low for too long. + 2. The Action: The nucleus "shships" more VGCC mRNA and protein (specifically the $\alpha_1$ subunit) back down the axon to the terminal. + 3. The Scale: This is the "Minutes and Beyond" territory. It is a slow, structural increase in the total number of channels to restore firing to a baseline level. +4. Summary of the "Minutes" Signal Logic +In your three-loop model, the ATP loop is likely the master regulator of these signals: + 1. Low ATP/High Residual $Ca^{2+}$ (Short term): Causes CDI (channels lock shut). + 2. Persistent $Ca^{2+}$ Overload (Minutes): Activates Ubiquitin ligases $\rightarrow$ Physical removal of VGCCs (Elimination). + 3. Chronic Silence/Low $Ca^{2+}$ Flux (Hours): Triggers Homeostatic Scaling $\rightarrow$ Trafficking of new VGCCs to the terminal (Addition). + --- **Behaviors**: diff --git a/neuron/presynapse.md b/neuron/presynapse.md index 90c7119..077cb58 100644 --- a/neuron/presynapse.md +++ b/neuron/presynapse.md @@ -419,27 +419,27 @@ tuner: VGCC-PRE-TUN tub_intricated: ``` -#### CheckPossibleTun:contexting +#### CheckVgccPreTun:contexting ```Gen -contexting: CheckPossibleTun +contexting: CheckVgccPreTun contained_by: VGCC-PRE-TUN in_context: TunPossible_ctx rf: ( active: 60x ) condition: - out_context: TunPreVcgg + out_context: TryTunPreVcgg_ctx ``` -#### interacting +#### PossibleVgccPreTun: interacting ```Gen -interacting: Tun +interacting: PossibleVgccPreTun contained_by: VGCC-PRE-TUN - in_context: TunPreVcgg - rf: ( active: x ) + in_context: TryTunPreVcgg_ctx + rf: ( active: 10x ) hypothesis: action: