Intracellular organization in cell polarity – placing organelles into the polarity loop

Abstract

Many studies have investigated the processes that support polarity establishment and maintenance in cells. On the one hand, polarity complexes at the cell cortex and their downstream signaling pathways have been assigned as major regulators of polarity. On the other hand, intracellular organelles and their polarized trafficking routes have emerged as important components of polarity. In this Review, we argue that rather than trying to identify the prime ‘culprit’, now it is time to consider all these players as a collective. We highlight that understanding the intimate coordination between the polarized cell cortex and the intracellular compass that is defined by organelle positioning is essential to capture the concept of polarity. After briefly reviewing how polarity emerges from a dynamic maintenance of cellular asymmetries, we highlight how intracellular organelles and their associated trafficking routes provide diverse feedback for dynamic cell polarity maintenance. We argue that the asymmetric organelle compass is an indispensable element of the polarity network.

Persistent cell migration emerges from a coupling between protrusion dynamics and polarized trafficking

“…To conclude, our present work focused on the coupling between protrusion dynamics and polarized trafficking. Many other functional units supporting cell polarity are likely to be involved (Vaidžiulyte et al, 2019), and it will be interesting to see in future studies how other coupling mechanisms can contribute to the robustness of cell polarity during persistent migration. Additionally, it would be of interest to see how our conclusions can be extended to other types of migration, such as the amoeboid one.…”

“…Regardless of the propulsive force or single/collective mode of migration, cells polarize to move (Rappel and Edelstein-Keshet, 2017). This is characterized by an asymmetric shape and distribution of proteins, organelles and lipids, as well as differential activities at the two extreme sides of the cell (Vaidžiulyte et al, 2019). This polarity allows cells to spatially segregate propulsive and contractile forces in order to move their body forward.…”

“…Based on pioneering work in yeast (reviewed in (Chiou et al, 2017)), cell polarity could be considered as an emergent property based on the coupling of high-level cellular functions, rather than being attributed to one specific pathway or to one single ‘culprit’ protein (Vaidžiulyte et al, 2019). Similarly, the emergence of persistency in cell migration could also rely on the coupling of high-level cellular functions.…”

Born to Run? Diverse Modes of Epithelial Migration

“…As a result of the establishment of this signaling, front-rear polarity is set up: on the cell membrane surface, PIP3 marks the front, in part due to localized activity of PI3 Kinase in the front, and PIP2 marks the rear. At the level of cytoskeleton arrangements, the lamellipodia-based actin network lies in the front, whereas cortical actin and stress-fiber-based actin bundles mark the rear (Ridley et al, 2003;Vaidziulyte et al, 2019). The microtubule network is also polarized, with the microtubule organizing center (MTOC) lining up with the direction of migration either directly in the front or the back of the nucleus (Figure 2) (Zhang and Wang, 2017).…”

Loss of cell–cell and cell–substrate contacts in single pancreatic β‐cells divert insulin release to intracellular vesicular compartments

“…When removed from their original environment, cells encounter different changes, including loss of cell–cell and cell–substrate contacts as well as interaction with their extracellular matrix. In most cases, these changes lead to rearrangement of cytoplasmic and membrane components that impairs intracellular trafficking and disturbs cell polarity and identity [Honda 2017; Vaidziulyte et al., 2019]. One of the common traits seen in dissociated epithelial cells with loss of cell–cell and cell–substrate contacts is intracellular vacuolation.…”