Characterisation of the non-muscle α-actinins

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dc.contributor.advisor Young, Paul en
dc.contributor.author Foley, Kate
dc.date.accessioned 2013-07-16T12:56:55Z
dc.date.available 2014-07-17T04:00:06Z
dc.date.issued 2013
dc.date.submitted 2013
dc.identifier.citation Foley, K. 2013. Characterisation of the non-muscle α-actinins. PhD Thesis, University College Cork. en
dc.identifier.endpage 182
dc.identifier.uri http://hdl.handle.net/10468/1180
dc.description.abstract Actinins are cytoskeleton proteins that cross-link actin filaments. Evolution of the actinin family resulted in the formation of Ca++-insensitive muscle isoforms (actinin-2 and- 3) and Ca++-sensitive non-muscle isoforms (actinin-1 and -4) with regard to their actin-binding function. Despite high sequence similarity, unique properties have been ascribed to actinin-4 compared with actinin-1. Actinin-4 is the predominant isoform reported to be associated with the cancer phenotype. Actinin-4, but not actinin-1, is essential for normal glomerular function in the kidney and and is able to translocate to the nucleus to regulate transcription. To understand the molecular basis for such isoform-specific functions I have comprehensively compared these proteins in terms of localisation, migration, alternative splicing, actin-binding properties, heterodimer formation and molecular interactions for the first time. This work characterises a number of commercially available actinin antibodies and in doing so, identifies actinin-1, -2 and -4 isoform-specific antibodies that enabled studies of actinin expression and localisation. This work identifies the actinin rod domain as the predominant domain that influences actinin localisation however localisation is likely to be effected by the entire actinin protein. si-RNA- mediated knockdown of actinin-1 and -4 did not affect migration in a number of cell lines highlighting that migration may only require a fraction of total non-muscle actinin levels. This work finds that the Ca++-insensitive variant of actinin-4 is expressed only in the nervous system and thus cannot be regarded as a smooth muscle isoform, as is the case for the Ca++-insensitive variant of actinin-1. This work also identifies a previously unreported exon 19a+19b expressing variant of actinin-4 in human skeletal muscle. This work finds that alternative splice variants of actinin-1 and -4 are co-expressed in a number of tissues, in particular the brain. In contrast to healthy brain, glioblastoma cells express Ca++-sensitive variants of both actinin-1 and -4. Actin-binding properties of actinin-1 and -4 are similar and are unlikely to explain isoform-specific functions. Surprisingly, this work reveals that actinin-1/-4 heterodimers, rather than homodimers, are the most abundant form of actinin in many cancer cell lines. Taken together this data suggests that actinin-1 and -4 cannot be viewed as distinct entities from each other but rather as proteins that can exist in both homodimeric and heterodimeric forms. Finally, this work employs yeast two-hybrid and proteomic approaches to identify actinin-interacting proteins. In doing so, this work identifies a number of putative actinin-4 specific interacting partners that may help to explain some of the unique functions attributed the actinin-4. The observation of alternative splice variants of actinin-1 and -4 combined with the observed potential of these proteins to form homodimers and heterodimers suggests that homodimers and heterodimers with novel actin-binding properties and interaction networks may exist. The ability to behave in this manner may have functional implications. This may be of importance considering that these proteins are central to such processes as cell migration and adhesion. This significantly alters our view of the non-muscle actinins. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2013, Kate Foley en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Actinin-1 en
dc.subject Actinin-4 en
dc.subject Non-muscle actinin en
dc.subject Actin-binding / bundling en
dc.subject Actinin heterodimer en
dc.subject.lcsh Cytoskeleton en
dc.subject.lcsh Cancer--Molecular aspects en
dc.subject.lcsh Cytology en
dc.title Characterisation of the non-muscle α-actinins en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.description.version Accepted Version
dc.contributor.funder Health Research Board en
dc.description.status Not peer reviewed en
dc.internal.school Biochemistry en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false *
dc.check.entireThesis Entire Thesis Restricted
dc.check.embargoformat Both hard copy thesis and e-thesis en
ucc.workflow.supervisor cora@ucc.ie *


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