Biology subjects

Tempes, A.

Publications and source records attributed to Tempes, A..

3 recordsLinked to original sources

bioRxiv2025

p70S6 kinase-dependent phosphorylation of the μ2 subunit of the AP2 adaptor complex is needed for clathrin-mediated endocytosis.

Clathrin-mediated endocytosis (CME) internalizes cell-surface receptors via clathrin-coated invaginations of the plasma membrane. Both clathrin and endocytic cargo are recruited to these sites by the adaptor protein complex AP2. AP2 cycles between a closed cytoplasmic conformation and an open membrane-bound state, and efficient CME requires both conformations and their dynamic interconversion. The mechanisms regulating these conformational changes, which include post-translational modifications of the AP2, remain incompletely understood. Here, we report that p70S6 kinase phosphorylates the {micro}2 subunit of the AP2 and that the phosphorylation of serine 45 (S45) depends on p70S6K activity. Loss of S45-{micro}2 phosphorylation results in decreased internalization of canonical CME cargo such as transferrin and PDGF receptors. In Caenorhabditis elegans, lack of S45-{micro}2 phosphorylation produces directionally similar but markedly weaker phenotypes than AP2 loss of function. Live imaging and in silico dynamic modelling suggest that S45-2 phosphorylation has impact on the conformational changes of the AP2 complex. These findings identify a p70S6K-dependent mechanism that modulates AP2 function and further strengthen the importance of post-translational regulation in controlling CME. Summary statementClathrin-mediated endocytosis is essential for receptor internalization and cell signaling. This study identifies a novel regulatory mechanism in which p70S6K-mediated phosphorylation of the AP2 subunit 2 at Ser45 modulates AP2 conformational dynamics and facilitates receptor endocytosis.

cell biology↗

bioRxiv2022

Dynactin interaction with AP-2 adaptor complex requires CLIP-170 and autophagy

The endocytic adaptor protein 2 (AP-2) complex binds dynactin as part of its noncanonical function, which is necessary for dynein-driven autophagosome transport along microtubules in neuronal axons. The absence of this AP-2-dependent transport causes neuronal morphology simplification and neurodegeneration. The mechanisms that lead to formation of the AP-2-dynactin complex have not been studied to date. However, the inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) enhances the transport of newly formed autophagosomes by influencing the biogenesis and protein interactions of Rab-interacting lysosomal protein (RILP), another dynein cargo adaptor. We tested effects of mTORC1 inhibition on interactions between the AP-2 and dynactin complexes, with a focus on their two essential subunits, AP-2{beta} and p150Glued. We found that the mTORC1 inhibitor rapamycin enhanced p150Glued-AP-2{beta} complex formation in both neurons and non-neuronal cells. Additional analysis revealed that the p150Glued-AP-2{beta} interaction was indirect and required integrity of the dynactin complex. In non-neuronal cells rapamycin-driven enhancement of the p150Glued-AP-2{beta} interaction also required the presence of cytoplasmic linker protein 170 (CLIP-170), the activation of autophagy, and an undisturbed endolysosomal system. The rapamycin-dependent p150Glued-AP-2{beta} interaction occurred on lysosomal-associated membrane protein 1 (Lamp-1)-positive organelles but without the need for autolysosome formation. Rapamycin treatment also increased the acidification and number of acidic organelles and increased speed of the long-distance retrograde movement of Lamp-1-positive organelles. Altogether, our results indicate that autophagy regulates the p150Glued-AP-2{beta} interaction, possibly to coordinate sufficient motor-adaptor complex availability for effective lysosome transport.

cell biology↗

bioRxiv2022

Rab11 regulates autophagy at dendritic spines in an mTOR- and NMDA-dependent manner

Synaptic plasticity is a process that shapes neuronal connections during neurodevelopment, learning, and memory. Autophagy is a mechanism that allows cells to degrade their unnecessary or dysfunctional components. Autophagosomes appear at dendritic spines in response to plasticity-inducing stimuli. Autophagy defects contribute to altered dendritic spine development, autistic-like behavior in mice, and neurological disease. While several studies explored the involvement of autophagy in synaptic plasticity, the steps preceding autophagosome emergence at the postsynapse remain unknown. Here we show a postsynaptic association of autophagy-related protein 9A (Atg9A), known to be involved in the initial stages of autophagosome formation, with Rab11, a small GTPase that regulates endosomal trafficking. Rab11 activity is necessary for the maintenance of Atg9A-positive structures at dendritic spines. Inhibition of mTOR increased Rab11 and Atg9A interaction and increased the emergence of autophagosomes in dendritic spines when coupled to NMDA receptor stimulation. Dendritic spines with newly formed autophagosomes were more resistant to NMDA-induced morphologic change. These results collectively suggest that autophagy initiation in dendritic spines depends on an activity-dependent Rab11a-Atg9A interaction regulated by mTOR.

neuroscience↗