Spatial Organization of Biological Fuctions | BPS Thematic Meeting

Spatial Organization of Biological Functions Meeting

Thursday Speaker Abstracts

TBD Pramod Pullarkat Ramen Research Institute, India No Abstract

SURFACE CHARGE REWIRES A LIPID–RAB–CYTOSKELETAL NETWORK TO STEER INTRACELLULAR FATE OF NANOPARTICLES Suchismita Bhowmik 1 ; Dhirendra S Katti 1 ; Nitin Mohan 1 ; 1 IIT Kanpur, BSBE, Kanpur, India Nanoparticle-based drug delivery is redefining precision medicine; however, their efficacy is shaped by how these carriers interact with cellular machinery. Once internalized, nanoparticles are sorted and transported through distinct endosomal pathways based on their physicochemical properties. We aim to uncover the cellular mechanisms that direct nanoparticles to specific intracellular fates and identify druggable targets that can augment drug delivery efficiency. Using super-resolution and live-cell imaging, we investigated how negatively charged bare(uncoated)mesoporous silica nanoparticles (MSNs) and positively charged chitosan-coated MSNs are differentially sorted and trafficked within epithelial cells. We found that surface charge had a striking effect on early intracellular behavior. Within one hour of internalization, bare MSNs moved retrogradely (toward the nucleus), while chitosan-coated MSNs displayed anterograde movement (towards cell periphery)—suggesting opposite sorting cues. This spatial divergence pointed to involvement of distinct membrane identities presumably of phosphoinositides (PI). Indeed, bare MSNs were enriched in PI3P-positive compartments, while chitosan-coated MSNs localized to PI4P-positive ones. Since PI3P is a hallmark of early endosomes (EEs) and PI4P is associated with recycling endosomes and the Golgi, our results indicated that MSNs of different charge engage distinct endocytic pathways. STORM imaging revealed that Rab5, a key EE marker, exhibited differential nanoscale clustering depending on MSN charge, further confirming charge-mediated membrane alterations. Notably, both types of MSNs altered EE motility, affecting speed, run length, and pause frequency in a charge-specific manner. Given that endosomal positioning and transport are driven by microtubules, we examined cytoskeletal engagement. Cytoskeletal analysis revealed bare MSNs preferentially associated with detyrosinated microtubules, a stable subset linked to long-range transport. Together, these results reveal that nanoparticle surface charge programs their intracellular itinerary by rewiring the lipid–Rab–cytoskeletal network. This network acts as a tunable interface, offering opportunities to control nanoparticle fate within cells and improve drug delivery efficacy.

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