Biology subjects

Mehrabi, A.

Publications and source records attributed to Mehrabi, A..

3 recordsLinked to original sources

bioRxiv2025

AMPK Repositions Early Endosomes via Gapex-5 to Promote Delivery of Iron to Mitochondria

The regulation of the spatial organization of organelles within cells is critical for coordinating signaling, membrane traffic, and metabolite exchange. Metabolic cues regulate the position and function of lysosomes, yet whether and how metabolic signals may similarly regulate other organelles such as early endosomes (EEs) remains unclear. We find that AMP-activated protein kinase (AMPK), a key regulator of metabolic homeostasis activated in response to nutrient scarcity, triggers movement of EEs to the perinuclear region of cells, leading to enhanced proximity of endosomes to mitochondria and increased delivery of iron to mitochondria. The movement of EEs and increased mitochondrial iron content elicited by AMPK activation requires Gapex-5, a GEF for the early endosome Rab5 previously shown to be an AMPK substrate. These findings reveal a mechanism by which AMPK reprograms endosome positioning to facilitate inter-organelle communication and iron delivery to mitochondria to support metabolic adaptation under conditions of nutrient scarcity.

cell biology↗

bioRxiv2025

NCK adaptor proteins regulate clathrin-coated pit dynamics and EGF-stimulated PI3K-Akt signaling

The epidermal growth factor (EGF) receptor (EGFR) promotes cell growth, proliferation, and survival. EGF binding to EGFR activates receptor kinase activity, leading to membrane recruitment of class IA phosphoinositide-3-kinase (PI3K), thus activating Akt signaling. Clathrin-coated pits (CCPs) are plasma membrane endocytic structures that are enriched in signaling intermediates and regulate in EGF-stimulated Akt activation. The mechanisms and impact of recruitment of certain signaling molecules within the PI3K-Akt pathway to CCPs remains poorly understood. Using total internal reflection fluorescence microscopy (TIRFM), we observed that the adaptor proteins Nck1 and Nck2 are enriched within CCPs and regulate early CCP formation and maturation. Nck1 and Nck2 each support EGF-stimulated Akt phosphorylation. Notably, EGF stimulation triggers Nck-dependent enrichment of PI3K within CCPs, and perturbation of Nck adaptors suppressed cell proliferation and survival. This study identifies novel functions for Nck adaptor proteins in EGFR-mediated recruitment of PI3K-Akt signals within CCPs, Akt activation, and cell physiology.

cell biology↗

bioRxiv2024

Cargo-selective regulation of clathrin-mediated endocytosis by AMP-activated protein kinase

The cell surface abundance of many proteins is controlled by clathrin-mediated endocytosis (CME). CME is driven by the assembly of clathrin and other proteins on the inner leaflet of the plasma membrane into clathrin-coated pits (CCPs). Regulation of CCP dynamics allows for control of the function of specific cell surface proteins, impacting a range of cellular outcomes. AMP-activated protein kinase (AMPK) becomes activated upon metabolic insufficiency and facilitates cellular adaptation to nutrient stress. Here, we examined how AMPK regulates CME and the cell surface membrane traffic of {beta}1-integrin. We find that AMPK controls CCP dynamics and regulates the abundance of the endocytic adaptor protein Dab2 within CCPs in a manner that requires the GTPase Arf6, thus selectively promoting the CCP recruitment and internalization of {beta}1-integrin. This reveals a novel signaling pathway for cargo-selective metabolic regulation of CME by AMPK, impacting the function of cell surface proteins such as integrins.

cell biology↗