Cell patterning by secretion-induced plasma membrane flows

Abstract

Exocytosis causes bulk membrane flows that drag associated proteins and form a negative feedback restricting the exocytic site.

Going with the membrane flow: the impact of polarized secretion on bulk plasma membrane flows

“…Tip‐growing walled cells (for instance many fungi and plant cells such as pollen tubes or root hairs) exhibit highly polarized secretion at their growing pole(s), which leads to a substantial excess of membrane exocytosis relative to the amount of new membrane required for cell growth, perhaps required to deliver sufficient cell wall remodeling material. In fission yeast cells, we and others estimated a 75–80% excess [ 1 , 2 ], with similar estimations in budding yeast [ 3 ]. Excess of at least 12.5% has also been estimated in the filamentous fungus Neurospora crassa [ 4 ].…”

“…The cell poles and medial division site are regions of new membrane and cell wall material delivery by polarized secretion. Using the CRY2‐CIBN optogenetic system, we recently revealed bulk membrane flows from secretion sites [ 1 ]. In our setup, the CIBN ligand associates with the plasma membrane peripherally by linkage with a small binding peptide (Fig.…”

“…In S . pombe , endocytosis occurs at zones of polarized secretion, but over a wider region [ 1 , 6 ]; in S . cerevisiae , endocytosis forms a ring around the secretion site at the time of bud emergence [ 7 , 8 ]; in filamentous fungi, the zone of endocytosis is largely distinct from the secretion zone, forming a collar around the exocytic apical zone (reviewed in [ 9 ]).…”

“…Similarly, exo‐ and endocytosis sites overlap at the apex of pollen tubes [ 10 ], but these display a clear sub‐apical region where endocytosis takes place [ 11 , 12 ], suggesting an organization very similar to that observed in filamentous fungi. In this configuration, computational simulations showed that membrane flows would occur even without net membrane growth [ 1 ]. The strongly polarized secretion and wider zone of membrane retrieval predicts that membrane flows are widely present in tip‐growing fungal and plant cells (Fig.…”

“…In fission yeast, secretory vesicles are targeted along the cleavage furrow and at the rim of the division plane through distinct tethering complexes [ 19 ]. The location of endocytosis has not been precisely mapped, but, at least in yeast, the region is wider than that of exocytosis [ 1 ]. In these cells, we observed that membrane‐associated proteins deplete from the division site and display long‐range retrograde movements, suggesting long‐range bulk flows.…”