A role for myosin VII in dynamic cell adhesion

Tuxworth, Richard I.; Weber, Igor; Wessels, Deborah; Addicks, Gregory C.; Soll, David R.; Gerisch, Günther; Titus, Margaret A.

doi:10.1016/s0960-9822(01)00097-5

Cited by 161 publications

(220 citation statements)

References 53 publications

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“…Blebbistatin inhibits ingestion of beads but not their adherence to the cell surface (Fig. 7D), which is inhibited in myosin VII-null cells (12,13). Expression of inactive myosin II (E476K) in HS1 cells also inhibits macropinocytosis (Ϸ50%) and phagocytosis (Ϸ70%) (Fig.…”

Section: Effect Of Blebbistatin On Myosin Ii-independent Activities: mentioning

confidence: 93%

Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium

Shu

Liu

Korn

2005

Proc. Natl. Acad. Sci. U.S.A.

101

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Blebbistatin, a cell-permeable inhibitor of class-II myosins, was developed to provide a tool for studying the biologic roles of myosin II. Consistent with this use, we find that blebbistatin inhibits three myosin II-dependent processes in Dictyostelium (growth in suspension culture, capping of Con A receptors, and development to fruiting bodies) and does not inhibit growth on plates, which does not require myosin II. As expected, macropinocytosis (myosin I-dependent), contractile vacuole activity (myosin V-dependent), and phagocytosis (myosin VII-dependent), none of which requires myosin II, are not inhibited by blebbistatin in myosin II-null cells, but, unexpectedly, blebbistatin does inhibit macropinocytosis and phagocytosis by cells expressing myosin II. Expression of catalytically inactive myosin II in myosin II-null cells also inhibits macropinocytosis and phagocytosis. Both blebbistatin-inhibited myosin II and catalytically inactive myosin II form cytoplasmic aggregates, which may be why they inhibit myosin II-independent processes, but neither affects the distribution of actin filaments in vegetative cells or actin and myosin distribution in dividing or polarized cells. Blebbistatin also inhibits cell streaming and plaque expansion in myosin II-null cells. Our results are consistent with myosin II being the only Dictyostelium myosin that is inhibited by blebbistatin but also show that blebbistatininactivated myosin II inhibits some myosin II-independent processes and that blebbistatin inhibits other activities in the absence of myosin II.phagocytosis ͉ macropinocytosis ͉ cell streaming ͉ development B lebbistatin (1), a cell-permeable inhibitor of myosin II ATPase activity, promises to be a very useful tool for identifying and studying myosin II-dependent processes in cells. As for any pharmacologic agent, however, extended use of blebbistatin will depend on the specificity and generality of its inhibition of class-II myosins. Thus far, blebbistatin's effect has been tested in vitro (1, 2) on only a few representatives of four of the 18 myosin classes that, together, contain Ͼ200 myosins. Blebbistatin inhibits myosin II from striated muscle, vertebrate nonmuscle cells, and Dictyostelium by Ϸ95%, with an IC 50 of 0.5-5 M. Smooth muscle and Acanthamoeba myosin II are only incompletely inhibited at blebbistatin concentrations as high as 160 M, with IC 50 values of Ϸ80 M, and blebbistatin does not inhibit either rat myosin Ib, Acanthamoeba myosin IC, mouse myosin V, or bovine myosin X. It is not practical to test the blebbistatin sensitivity of all of the myosins or to determine whether blebbistatin might inhibit enzymes other than myosins, whether some functions of myosin II might not require enzymatic activity (and, therefore, not be inhibited by blebbistatin), or whether enzymatically inactive myosin II might directly or indirectly affect any non-myosin II-dependent cell function in all cells.The social amoeba Dictyostelium discoideum provides a useful system for assessing some of these variables. Dictyos...

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Section: Effect Of Blebbistatin On Myosin Ii-independent Activities: mentioning

confidence: 93%

Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium

Shu

Liu

Korn

2005

Proc. Natl. Acad. Sci. U.S.A.

101

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“…As detailed above, several other gene products also play a critical role in cellular adhesion in Dictyostelium, in particular myosin VII and talin (Titus, 1999;Niewohner et al, 1997;Tuxworth et al, 2001). To compare their role in adhesion with the function of Phg2, we generated the corresponding disruption mutants in our Dictyostelium laboratory strain (DH1-10), and measured the adhesion of phg1, phg2, myoVII, and talin cells to a glass substrate in HL5 medium.…”

Section: Phg2 a Kinase Involved In Phagocytosismentioning

confidence: 99%

“…However, the phenotype of phg2 mutants could not be accounted for entirely by a decrease in the level of talin, because the amount of talin is only slightly decreased in phg2 mutant cells, and because phg2 mutant cells present phenotypes not observed in talin mutant cells. In addition it is unlikely that Phg2 forms a stable complex with either myosinVII or talin, because Phg2 is evenly distributed at the cell membrane, whereas myosin VII and talin concentrate at sites of active actin remodeling, i.e., at the tip of filopods and at the leading edge of migrating cells (Kreitmeier et al, 1995;Tuxworth et al, 2001). Thus, an interaction between Phg2 and these cytoskeletal proteins could only be transient or indirect.…”

Section: Phg2 Plays a Specific Role In The Organization Of The Actin mentioning

confidence: 99%

“…For example, the actin-binding protein talin is necessary for phagocytosis and adhesion in Dictyostelium (Niewohner et al, 1997). Dictyostelium myosin VII null mutants also have defects in both cell-cell and cell-substrate adhesion (Tuxworth et al, 2001). Homologues of VASP and small GTPbinding proteins of the ras family also have been identified in Dictyostelium, and mutant phenotypes are indicative of roles in adhesion and regulation of the actin cytoskeleton Lim et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Phg2, a Kinase Involved in Adhesion and Focal Site Modeling inDictyostelium

Gebbie

Benghezal

Cornillon

et al. 2004

MBoC

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The amoeba Dictyostelium is a simple genetic system for analyzing substrate adhesion, motility and phagocytosis. A new adhesion-defective mutant named phg2 was isolated in this system, and PHG2 encodes a novel serine/threonine kinase with a ras-binding domain. We compared the phenotype of phg2 null cells to other previously isolated adhesion mutants to evaluate the specific role of each gene product. Phg1, Phg2, myosin VII, and talin all play similar roles in cellular adhesion. Like myosin VII and talin, Phg2 also is involved in the organization of the actin cytoskeleton. In addition, phg2 mutant cells have defects in the organization of the actin cytoskeleton at the cell-substrate interface, and in cell motility. Because these last two defects are not seen in phg1, myoVII, or talin mutants, this suggests a specific role for Phg2 in the control of local actin polymerization/depolymerization. This study establishes a functional hierarchy in the roles of Phg1, Phg2, myosinVII, and talin in cellular adhesion, actin cytoskeleton organization, and motility.

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“…Likewise, phg1 cells, generated by insertional mutagenesis, have defective phagocytosis that coincides with faulty adhesion (Cornillon et al, 2000). Mutants of cortical cytoskeletal proteins such as talin (Niewö hner et al, 1997) and myosin VII (Tuxworth et al, 2001) similarly show a tight coupling of phagocytosis and adhesion. Because gp130-null cells had 50% of the cellsubstrate adhesion of the parent DH1 cells, but were phagocytically functional, it appeared that gp130 participated in a cell-substrate adhesion mechanism different from the sadA and phg1 proteins, and also distinct from that used in the recognition of Klebsiella aerogenes and E. coli bacteria.…”

Section: Function Of Gp130mentioning

confidence: 99%

Glycoprotein gp130 ofDictyostelium discoideumInfluences Macropinocytosis and Adhesion

Chia

Gomathinayagam

Schmaltz

et al. 2005

MBoC

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Glycoprotein gp130, found on the plasma membrane of Dictyostelium discoideum amoebae, was postulated previously to play a role in phagocytosis. The gene for gp130 was cloned and when translated, yielded a 768 amino acid preproprotein of 85.3 kDa. It had nearly 40% similarity to the 138 kDa family of glycoproteins implicated in sexual cell fusion during macrocyst formation in D. discoideum. The difference between the calculated size and observed M r of 130 kDa on protein gels likely was due to N-glycosylation that was confirmed by lectin blots. Consistent with its surface-exposure, an antibody raised against recombinant protein stained the plasma membrane of D. discoideum amoebae. Gp130 and its transcripts were high during axenic growth of cells, but relatively low during growth on bacteria. The gene for gp130 was disrupted and cell lines lacking the glycoprotein were efficient phagocytes, indicating that gp130 was dispensable for phagocytosis. Gp130-null cells were similar in size to parent DH1 cells, had enhanced macropinocytosis and grew faster to higher densities. They also exhibited weaker cell-substrate adhesion but displayed greater cell-cell cohesion. Collectively, the data indicated that gp130 influenced macropinocytosis and played a role in adhesion during vegetative growth. INTRODUCTIONThe processes of phagocytosis, cell-cell and cell-substrate adhesion share a common initial event of recognition, whether it is of specific ligands or the chemical properties of the partner(s) in the interaction. With the long-term aim of understanding the mechanism of phagocytosis at the molecular level, particularly the early steps of recognition and binding, we have focused on surface-exposed molecules of the phagocytically active amoebae of Dictyostelium discoideum. D. discoideum cells are studied also for the related processes of motility and aggregation. When starved, individual but clonal cells coalesce into multicellular structures that, within a day, differentiate into fruiting bodies called sorocarps. Cell-cell recognition and adhesion are vital aspects of this developmental progression, and researchers have established that cell-surface molecules, including gp24 (Knecht et al., 1987;Loomis, 1988;Brar and Siu, 1993), gp80 (Muller and Gerisch, 1978;Noegel et al., 1986), and gp150 (Gao et al., 1992;Wang et al., 2000), are mediating these interactions (reviewed in Kessin, 2001 andSiu et al., 2004). An understanding of the plasma membrane molecules involved in adhesive events during phagocytosis and motility of vegetative amoebae is emerging with the recent identification of cell-substrate adhesion molecule, sadA (Fey et al., 2002) and the phg1 family of transmembrane 9 proteins (Cornillon et al., 2000;Benghezal et al., 2003).In this study, we present evidence that a plasma membrane glycoprotein gp130 also played a role in cell-substrate adhesion during vegetative growth. Postulated to be a phagocytosis receptor (Chia, 1996), gp130 is possibly the same molecule as gp126, a surface-exposed glycoprotein suggested to ...

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A role for myosin VII in dynamic cell adhesion

Abstract: Myosin VII plays an important role in mediating the initial binding of cells to substrata, a novel role for an unconventional myosin.

Cited by 161 publications

References 53 publications

Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium

Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium

Phg2, a Kinase Involved in Adhesion and Focal Site Modeling inDictyostelium

Glycoprotein gp130 ofDictyostelium discoideumInfluences Macropinocytosis and Adhesion

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