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M Krendel

Publications and source records attributed to M Krendel.

4 recordsLinked to original sources
PubMed2000

Characterization of sea urchin unconventional myosins and analysis of their patterns of expression during early embryogenesis.

Early sea urchin development requires a dynamic reorganization of both the actin cytoskeleton and cytoskeletal interactions with cellular membranes. These events may involve the activities of multiple members of the superfamily of myosin motor proteins. Using RT-PCR with degenerate myosin primers, we identified 11 myosin mRNAs expressed in unfertilized eggs and coelomocytes of the sea urchin Strongylocentrotus purpuratus. Seven of these sea urchin myosins belonged to myosin classes Igamma, II, V, VI, VII, IX, and amoeboid-type I, and the remaining four may be from novel classes. Sea urchin myosins-V, -VI, -VII, and amoeboid-type-I were either completely or partially cloned and their molecular structures characterized. Sea urchin myosins-V, -VI, -VII, and amoeboid-type-I shared a high degree of sequence identity with their respective family members from vertebrates and they retained their class-specific structure and domain organization. Analysis of expression of myosin-V, -VI, -VII, and amoeboid-type-I mRNAs during development revealed that each myosin mRNA displayed a distinct temporal pattern of expression, suggesting that myosins might be involved in specific events of early embryogenesis. Interestingly, the onset of gastrulation appeared to be a pivotal point in modulation of myosin mRNA expression. The presence of multiple myosin mRNAs in eggs and embryos provides insight into the potential involvement of multiple specific motor proteins in the actin-dependent events of embryo development.

Amino Acid Sequence↗
PubMed1999

Myosin-dependent contractile activity of the actin cytoskeleton modulates the spatial organization of cell-cell contacts in cultured epitheliocytes.

The spatial organization of cell-cell adherens junctions is distinct in cultured cells from two different tissue types, specifically, epitheliocytes and fibroblasts. In epitheliocytes, contacts are localized tangentially, along contacting cell edges and in association with circumferential actin bundles. Contacts between fibroblasts are radially oriented; that is, they are perpendicular to the overlapping edges of the cells and are associated with straight bundles of actin filaments. In the present study, we establish that the spatial organization of cell-cell contacts in the epithelial cell line IAR-2 can be converted from the typical tangential pattern to the radial pattern observed in fibroblasts. This transition can be induced by treatment with two agents, phorbol 12-myristate 13-acetate and nocodazole, which have different modes of action. Inhibition of myosin contractility reverses tangential-to-radial conversion of cell-cell contacts. These data suggest that formation of radially aligned contacts depends on modulation of contractility within the actin cytoskeleton through the myosin motor protein. The results open the possibility that modulation of the spatial organization of cell-cell contacts may play important roles in regulating organization and physiological functions of epithelial tissues.

Actins↗
PubMed1998

Disassembly of actin filaments leads to increased rate and frequency of mitochondrial movement along microtubules.

In activated sea urchin coelomocytes, cytoplasmic organelles move along distinct actin and microtubule dependent pathways, actin-based motility is driven by an unconventional myosin, and microtubule disassembly does not effect actin-dependent organelle motility [D'Andrea et al., 1994: J. Cell Sci. 107:2081-2094]. Given the growing evidence for potential interactions between components of the actin and microtubule cytoskeletons, we examined the effect of actin filament disassembly on the movement of mitochondria along microtubules in activated coelomocytes. Coelomocytes treated with cytochalasin B (CB), to disrupt actin filaments, exhibited a thinning of the cytoplasm, enhanced lateral undulation of microtubules, and ceased centripetal cortical flow of actin. Interestingly, the loss of actin filaments resulted in a approximately 1.5-fold increase in the average velocity of outward and inward moving mitochondria and increased the frequency of centripetal movement. To test if enhanced motility along microtubules was a consequence of decreased actin-myosin interaction, coelomocytes were treated with 2,3-butanedione monoxime (BDM), a potent inhibitor of myosin activity [Cramer and Mitchison, 1995: J. Cell Biol. 131:179-189]. BDM inhibited all types of actin-based motility observed in these cells including retrograde cortical flow, protrusion and retraction of the cell edge, and movement of intracellular organelles. Surprisingly, BDM treatment stopped the movement of mitochondria in CB-exposed cells, suggesting that BDM can also act as an inhibitor of organelle movement along microtubules. Collectively, these data demonstrated that microtubule-dependent mitochondrial motility and microtubule movement were sensitive to changes in the assembly state of the actin cytoskeleton.

Actins↗