Target shape dependence in a simple model of receptor-mediated endocytosis and phagocytosis

TL;DR

This study investigates how particle shape influences receptor-mediated endocytosis and phagocytosis, revealing that shape significantly affects engulfment efficiency and that phagocytosis can handle a wider variety of shapes than other endocytic processes.

Contribution

The paper introduces a simple 1D and 2D model comparing shape-dependent engulfment behaviors in endocytosis and phagocytosis, highlighting the impact of shape on these processes.

Findings

Ellipsoids can be engulfed faster than spheres.

Phagocytosis accommodates a broader range of shapes.

Nonspherical particles are most efficiently engulfed tip-first or lying flat.

Abstract

Phagocytosis and receptor-mediated endocytosis are vitally important particle uptake mechanisms in many cell types, ranging from single-cell organisms to immune cells. In both processes, engulfment by the cell depends critically on both particle shape and orientation. However, most previous theoretical work has focused only on spherical particles and hence disregards the wide-ranging particle shapes occurring in nature, such as those of bacteria. Here, by implementing a simple model in one and two dimensions, we compare and contrast receptor-mediated endocytosis and phagocytosis for a range of biologically relevant shapes, including spheres, ellipsoids, capped cylinders, and hourglasses. We find a whole range of different engulfment behaviors with some ellipsoids engulfing faster than spheres, and that phagocytosis is able to engulf a greater range of target shapes than other types of endocytosis. Further, the 2D model can explain why some nonspherical particles engulf fastest (not at all) when presented to the membrane tip-first (lying flat). Our work reveals how some bacteria may avoid being internalized simply because of their shape, and suggests shapes for optimal drug delivery.