AI Insight
This study identifies Paralemmin-2 (Palm2) as a structural protein component of the axon initial segment (AIS) and nodes of Ranvier (NoR), specialized regions critical for nerve signal initiation and transmission. Palm2 depletion shortens the AIS and decreases neuronal excitability, while its overexpression disrupts the underlying periodic cytoskeleton by interfering with spectrin organization. Palm2 and its homolog Palm1 interact with a deubiquitinating enzyme (USP7), suggesting they regulate protein stability at these specialized axonal sites.
Why it matters
Understanding the molecular architecture of the AIS and nodes of Ranvier is essential for comprehending how neurons generate and propagate electrical signals. Disruptions in these structures are implicated in neurological disorders, so identifying components like Palm2 could provide new therapeutic targets for conditions affecting nerve conduction.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
The axon initial segment (AIS) and nodes of Ranvier (NoR) are essential for action potential initiation and propagation. They share many features of their molecular architecture, and their assembly mechanisms converge on the membrane-associated periodic skeleton (MPS). Here, we identify Paralemmin-2 (Palm2) as a component of both the AIS and NoR. Palm2 depletion shortens the AIS and reduces neuronal excitability. Endogenous Palm2 in the AIS is non-periodic, but upon overexpression it associates with the MPS, localizing to actin rings and reducing {beta}IV-spectrin abundance and periodicity. In NoR of the central and peripheral nervous system, Palm2 localizes to different subdomains – nodal or paranodal, respectively. Palm2, and its homolog Palm1, bind the deubiquitinase USP7, implicating paralemmins in proteostasis at the MPS. The complementary localizations of Palm2 and Palm1 at the AIS/NoR or axon shafts, respectively, parallel the distributions of {beta}-spectrin and ankyrin isoforms between these axonal compartments. We propose that Palm2 modulates the submembrane cytoskeleton and its membrane attachment, and thus contributes to the assembly, functioning and remodeling of the AIS and NoR.