Dynamin A, Myosin IB and Abp1 Couple Phagosome Maturation to F‐Actin Binding

Abstract

The role of actin, class I myosins and dynamin in endocytic uptake processes is well characterized, but their role during endo-phagosomal membrane trafficking and maturation is less clear. In Dictyostelium, knockout of myosin IB (myoB) leads to a defect in membrane protein recycling from endosomes back to the plasma membrane. Here, we show that actin plays a central role in the morphology and function of the endocytic pathway. Indeed, latrunculin B (LatB) induces endosome tubulation, a phenotype also observed in dynamin A (dymA)-null cells. Knockout of dymA impairs phagosome acidification, whereas knockout of myoB delays reneutralization, a phenotype mimicked by a low dose of LatB. As a read out for actindependent processes during maturation, we monitored the capacity of purified phagosomes to bind F-actin in vitro, and correlated this with the presence of actinbinding and membrane-trafficking proteins. Phagosomes isolated from myoB-null cells showed an increased binding to F-actin, especially late phagosomes. In contrast, early phagosomes from dymA-null cells showed reduced binding to F-actin while late phagosomes were unaffected. We provide evidence that Abp1 is the main F-actin-binding protein in this assay and is central for the interplay between DymA and MyoB during phagosome maturation.

Interplay between Clathrin and Rab5 Controls the Early Phagocytic Trafficking and Intracellular Survival of Brucella abortus within HeLa cells

“…Unlike the transient interaction of clathrin and Rab5 with BCVs, increased levels of dynamin, caveolin, F-actin, and Arp2/3 were observed in BCVs for an extended period of time. These results may indicate that these components have a variety of functions related to the transport and sorting of endocytic vesicles in addition to their roles in the formation of clathrin-coated vesicles (49,50). The association of BCVs with early endosomes is dependent on Rab5 and clathrin and accompanied by interactions with lipid rafts, dynamin, and cytoskeletal components.…”

The Balance in the Delivery of ER Components and the Vacuolar Proton Pump to the Phagosome Depends on Myosin IK in Dictyostelium

“…Other data support this hypothesis. Abp1 is the major F-actin binding player on phagosomes isolated from Dictyostelium in vitro and its absence might disorganize the dynamics of the actin network on the phagosome (18). Indeed, an increase in phagocytosis rates in knockdown of human Rab27a correlates with a quicker turnover of F-actin coating and degradation at the phagocytic cup (41).…”

“…On the other hand, actin polymerization and Abp1 play an active role in phagosome maturation. Indeed, the formation of a transient actin coat prevents phagosomelysosome fusion and delays phagocytosis (22) and the presence of Abp1 regulates phagosome binding to actin in vitro (18). Nevertheless, the impact of a regulatory switch of actin polymerization on the downstream maturation process has not been investigated.…”

“…Although the role of Abp1 in vesicle formation has been mainly studied during uptake at the plasma membrane, it might perform similar tasks on endomembranes. Indeed, Abp1 is the main phagosomal F-actin binding protein (18).…”

The Rac GEF ZizB regulates development, cell motility and cytokinesis in Dictyostelium

“…7). Interestingly, a similar cytokinesis defect was found in the dynamin-A-null strain (Gopaldass et al, 2012;Wienke et al, 1999). This phenotype also suggests a role for ZizB in regulation of the actin-myosin cytoskeleton involved in cell division .…”