Every cell in your body is, in a very real sense, eating. It is sampling the fluid around it, pulling in proteins, lipids, and signals it cannot otherwise reach, then deciding—through a cascade of lipid switches and tiny GTPase proteins—whether to digest what it has swallowed or to spit it back out. Meanwhile, in schoolyards from Santiago to Nayarit, a different kind of nutrition crisis is unfolding: children drinking caffeinated soft drinks before bed, sleeping under ten hours, and gaining weight at rates that will haunt their adult metabolisms. What connects the phosphoinositide chemistry of a macropinosome to a bag of chips in a Mexican fourth-grader's lunchbox is the same fundamental question that drives medicine: how does a living system decide what to take in, what to keep, and what to let go?
The week between October 3 and October 10, 2026, delivered an unusually rich cluster of papers that, taken together, sketch a picture of medicine operating at two scales simultaneously—the molecular and the populational, the organelle and the schoolyard. Five papers, spanning Nature, the Journal of Cell Science, and Archivos Latinoamericanos de Nutrición, remind us that the mechanisms governing a single vesicle's fate and the dietary patterns of 724 schoolchildren are, in the end, two chapters of the same story about how organisms acquire, process, and regulate the resources they need to survive.
The Immune Cell's Stomach: A Two-Step Switch That Decides Swallow or Recycle
Macropinocytosis is one of the most visually dramatic processes in cell biology. A cell extends its membrane into ruffled, cup-like protrusions, scoops up a generous volume of extracellular fluid, and seals it off into a giant vesicle called a macropinosome. Immune cells use this mechanism to sample their surroundings for antigens; cancer cells hijack it to slurp up nutrients in nutrient-poor tumour microenvironments. But what happens after the macropinosome pinches off? For a long time, the answer was murky.
Spangenberg, Moe, Ødegård-Fougner, and colleagues at the University of Oslo have now mapped the decisive fork in the road with striking clarity [4]. Their work in the Journal of Cell Science identifies a phosphoinositide-and-RAB switch that determines whether a newly formed macropinosome matures into an endosome or simply fuses back with the plasma membrane and releases its cargo. The linchpin is VPS34 (PIK3C3), a phosphatidylinositol 3-kinase that generates phosphatidylinositol 3-phosphate (PtdIns3P) on the macropinosomal membrane. When VPS34 is active, PtdIns3P accumulates, and this lipid recruits the small GTPase RAB5A along with its downstream effectors. RAB5A, in turn, establishes the endosomal identity of the vesicle, committing it to the maturation pathway toward late endosomes and lysosomes.
But when the team inhibited VPS34, the story flipped. Without PtdIns3P, RAB5A was not recruited. Instead, a different set of regulators—RAB8A, RAB10, RAB11A, and PtdIns4P—accumulated on the macropinosome. These are the classic machinery of endocytic recycling. The result: macropinosomes that should have matured into endosomes instead fused back with the plasma membrane, spilling their contents back into the extracellular space. Fluid-phase uptake dropped, and the cell effectively
References
- Joseph K. Rathkey, S. S. Choi, Vincent van Unen et al. (2026). Human lung organoid modelling of tissue-resident antiviral T cell responses. Nature.
- Guillermo Doménech-Asensi, Alba Manuela Durango Villadiego, Gaspar Ros (2026). Moringa oleifera: Revisión sobre aplicaciones y usos en alimentos. Archivos Latinoamericanos de Nutrición.
- Víctor Manuel Zamora-Gasga, Efigenia Montalvo‐González, Guadalupe Flavia Loarca-Piña et al. (2026). Dietary patterns, nutritional profile, and body mass index in Mexican schoolchildren: A cross-sectional study. Archivos Latinoamericanos de Nutrición.
- Hélène Spangenberg, Emilie Løgith Moe, Øyvind Ødegård‐Fougner et al. (2026). A phosphoinositide and RAB switch controls early macropinocytosis. Journal of Cell Science.
- Samuel Durán‐Agüero, Gustavo Andres Cediel Giraldo, Jerusa Brignardello Guerra (2026). Relationship between nutritional status and sleep duration in Chilean school-age children. Archivos Latinoamericanos de Nutrición.