Microenvironmental Regulation of Macropinocytosis Facilitates Extracellular Fluid Sampling

Microenvironmental Regulation of Macropinocytosis Facilitates Extracellular Fluid Sampling | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Biological Sciences - Article Microenvironmental Regulation of Macropinocytosis Facilitates Extracellular Fluid Sampling Jörg Renkawitz, Malte Braun, Rifat Reza, Petra Kameritsch, Mauricio Ruiz-Fernandez, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4223901/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Cells sense chemical and mechanical signals within their local microenvironment. To sample for chemical signals, cells employ bulk extracellular fluid uptake through macropinocytosis in a receptor-independent manner. Although macropinocytosis occurs in microenvironments of multicellular organisms, it remains largely unknown whether and how the microenvironment itself regulates fluid sampling. Here, we reveal that the microenvironmental properties regulate fluid sampling by macropinocytosis. Using macrophages as constitutively sampling immune cells, we discover that macropinocytosis in three-dimensional (3D) microenvironments is more efficient than on flat 2D surfaces. Enhanced macropinocytosis in 3D is driven by low adhesiveness to the cellular substrate, releasing the mechanical linkage between the cell and its surroundings, thereby facilitating the formation of actin-based membrane protrusions that sample the local substrate-free space. Mechanistically, we identify that the microenvironment regulates the utilization of macropinocytosis-competent actin networks, as the actin nucleating Arp2/3 complex and its regulator Hem1 particularly drive macropinocytosis in 3D. Our results establish microenvironmental properties as stimulators and regulators of macropinocytosis, providing important implications for fluid sampling during physiology, immunity, and diseases. Additionally, our findings identify a reciprocal relationship between the microenvironment and fluid sampling, wherein cells acquire information from the microenvironment by macropinocytosis, while this process, in turn, is regulated by the microenvironment. Biological sciences/Cell biology/Membrane trafficking Biological sciences/Cell biology/Cytoskeleton/Actin Biological sciences/Cell biology/Cell adhesion/Extracellular matrix Full Text Additional Declarations There is NO Competing Interest. Supplementary Files ExtendedDataMovie1.mp4 Extended Data Movie 1 ExtendedDataMovie2.mp4 Extended Data Movie 2 ExtendedDataMovie3.mp4 Extended Data Movie 3 ExtendedDataMovie4.mp4 Extended Data Movie 4 ExtendedDataMovie5.mp4 Extended Data Movie 5 ExtendedDataMovie6.mp4 Extended Data Movie 6 ExtendedDataMovie7.mp4 Extended Data Movie 7 ExtendedDataMovie8.mp4 Extended Data Movie 8 ExtendedDataMovie9.mp4 Extended Data Movie 9 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4223901","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Biological Sciences - Article","associatedPublications":[],"authors":[{"id":292327994,"identity":"dba0a9fb-2c6e-48ce-b2c0-3f1e4f123fe7","order_by":0,"name":"Jörg 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