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Biomedical subjects

Elizabeth Smythe

Publications and source records attributed to Elizabeth Smythe.

11 recordsLinked to original sources
PubMed2006

Actin regulation in endocytosis.

Increasing evidence from a variety of cell types has highlighted the importance of the actin cytoskeleton during endocytosis. No longer is actin viewed as a passive barrier that must be removed to allow endocytosis to proceed. Rather, actin structures are dynamically organised to assist the remodelling of the cell surface to allow inward movement of vesicles. The majority of our mechanistic insight into the role of actin in endocytosis has come from studies in budding yeast. Although endocytosis in mammalian cells is clearly more complex and subject to a greater array of regulatory signals, recent advances have revealed actin, and actin-regulatory proteins, to be present at endocytic sites. Furthermore, live cell imaging indicates that spatiotemporal aspects of actin recruitment and vesicle formation are likely to be conserved across eukaryotic evolution.

Actins↗
PubMed2006

Within the web: the family-practitioner relationship in the context of chronic childhood illness.

This hermeneutic phenomenological study explores the relationship between health professionals and families who have a child with a chronic illness. Study participants included 10 family groups who had a child with a chronic illness and 12 practitioners from the disciplines of nursing, medicine, dietetics, physiotherapy and speech therapy. Data were collected by narrative audiotaped interviewing. The results of this study revealed that chronic childhood illness 'throws' families and practitioners together into a web of relationships, which must work for the sake of the child. However, children are usually excluded from the relationship. To understand and manage the child's illness, practitioners and families 'go around' and act 'in-between' relationships. While the quality of the relationship from the family perspective is not essential, relationships are more successful when practitioners recognize the uniqueness of each family web. The nature of the relationship is often simple, yet it coexists with complexity.

Adaptation, Psychological↗
PubMed2005

Regulation of the clathrin-coated vesicle cycle by reversible phosphorylation.

Reversible phosphorylation has long been an attractive mechanism to control cycles of coat assembly and disassembly during clathrin-mediated endocytosis. Many of the coat proteins are phosphorylated in vivo and in vitro. Our work has focused on the role of phosphorylation of the mu2 subunit of AP-2 (adaptor protein 2), which appears to be necessary for efficient cargo recruitment. Studies to probe the regulation of mu2 phosphorylation demonstrated that clathrin is a specific activator of the mu2 kinase, and, in permeabilized cells, cargo sequestration, driven by exogenously added clathrin, results in elevated levels of m2 phosphorylation. Furthermore, phosphorylated mu2 is mainly associated with assembled clathrin in vivo and its steady-state level is strongly reduced in cells depleted of clathrin heavy chain. Our results imply a central role for clathrin in the regulation of cargo selection via modulation of phospho-mu2 levels. This is therefore a novel regulatory role for clathrin that is independent of its structural role and that provides elegant spatial control of AP-2 and cargo interactions, ensuring that AP-2 is only activated at the correct cellular location and in the correct functional context. Ongoing studies are exploring further the roles of reversible phosphorylation in the coated vesicle cycle.

Adaptor Protein Complex 2↗
PubMed2005

Multiple roles for cyclin G-associated kinase in clathrin-mediated sorting events.

Cyclin G-associated kinase (GAK), also known as auxilin 2, is a potential regulator of clathrin-mediated membrane trafficking. It possesses a kinase domain at its N-terminus that can phosphorylate the clathrin adaptors AP-1 and AP-2 in vitro. The GAK C-terminus can act as a cochaperaone in vitro for Hsc70, a heat-shock protein required for clathrin uncoating. Here we show that the specificity of GAK is very similar to that of adaptor-associated kinase 1, another mammalian adaptor kinase. We used siRNA to investigate GAK's in vivo function. We discovered that early stages of clathrin-mediated endocytosis (CME) were partially inhibited when GAK expression was knocked down. This defect was specifically caused by GAK knockdown because it could be rescued by expressing a rat GAK gene that could not be silenced by one of the siRNAs. To identify the GAK activity required during CME, we mutated the kinase domain and the J domain of the rat gene. Only GAK with a functional J domain could rescue the defect, suggesting that GAK is important for clathrin uncoating. Furthermore, we demonstrated that GAK plays a role in the clathrin-dependent trafficking from the trans Golgi network.

Animals↗
PubMed2003

Clathrin promotes incorporation of cargo into coated pits by activation of the AP2 adaptor micro2 kinase.

Endocytic cargo such as the transferrin receptor is incorporated into clathrin-coated pits by associating, via tyrosine-based motifs, with the AP2 complex. Cargo-AP2 interactions occur via the mu2 subunit of AP2, which needs to be phosphorylated for endocytosis to occur. The most likely role for mu2 phosphorylation is in cargo recruitment because mu2 phosphorylation enhances its binding to internalization motifs. Here, we investigate the control of mu2 phosphorylation. We identify clathrin as a specific activator of the mu2 kinase and, in permeabilized cells, we show that ligand sequestration, driven by exogenous clathrin, results in elevated levels of mu2 phosphorylation. Furthermore, we show that AP2 containing phospho-mu2 is mainly associated with assembled clathrin in vivo, and that the level of phospho-mu2 is strongly reduced in a chicken B cell line depleted of clathrin heavy chain. Our results imply a central role for clathrin in the regulation of cargo selection via the modulation of phospho-mu2 levels.

Adaptor Protein Complex 2↗
PubMed2003

The Ark1/Prk1 family of protein kinases. Regulators of endocytosis and the actin skeleton.

The Ark/Prk serine/threonine kinases initiate phosphorylation cycles that control the endocytic machinery in mammalian cells and in yeast, and the actin cytoskeleton in yeast. The members of this protein family are unified by homologies in their kinase domain, but are generally diverse in their other domains. The evolution of Ark/Prk family members in different organisms may have allowed the conserved role of the kinase domain, which is required for the phosphorylation of both endocytic and cytoskeletal components, to be coupled to other functional domains.

Actins↗
PubMed2003

Uncovering the meaning of 'being safe' in practice.

This paper moves away from the prevalent discourse of competence to consider the meaning of the experience of 'being safe' within the context of childbirth. It offers findings from a doctoral study, informed by the philosophies of Heidegger and Gadamer. Following ethical approval, the data was collected in New Zealand by tape-recorded interviews of 5 midwives, 4 obstetricians, 1 general practitioner and 10 women. The method was informed by van Manen. The findings reveal that in seeking the meaning of being safe one needs to be aware that the unsafety may already be present in the situation. Practitioners may be able to do little to rectify the unsafeness. There is, however, a spirit of safe practice, explicated in this paper, that is likely to make practice as safe as it can possibly be. Wise practitioners are ever mindful that a situation may be or become unsafe, and are always aware of their own limitations.

Female↗
PubMed2002

Regulating the clathrin-coated vesicle cycle by AP2 subunit phosphorylation.

Clathrin-coated pits form from the concerted assembly of many different protein components that interact with each other and with the lipid bilayer. When the coated pit pinches off to form a coated vesicle, the coat is removed to allow fusion of the endocytic vesicle with an early endosome, and the disassembled coat components can then recycle through the cytosol to participate in new rounds of coated pit formation. One potential mechanism to regulate the cycles of coat protein assembly and disassembly is reversible phosphorylation, particularly given that many of the coat components, such as the AP2 adaptor complex, are phosphorylated on multiple sites both in vitro and in vivo. Recent studies have provided particular insight into the role of phosphorylation of the cargo-binding micro2 subunit of AP2.

Adaptor Protein Complex 1↗
PubMed2002

Direct interactions between rab GTPases and cargo.

The rab family of small GTPases has numerous roles in intracellular transport including budding, tethering, and fusion of vesicles as well as organelle motility. New data show that cargo proteins are also rab effectors and can therefore regulate their own trafficking by direct interactions with the transport machinery.

Animals↗