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The functional interplay between TPRM7 channel-kinase autophosphorylation and its cellular regulation
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Cai, Na. The functional interplay between TPRM7 channel-kinase autophosphorylation and its cellular regulation. Retrieved from https://doi.org/doi:10.7282/T3FX7DWQ

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TitleThe functional interplay between TPRM7 channel-kinase autophosphorylation and its cellular regulation
NameCai, Na (author); Runnels, Loren W (chair); Walworth, Nancy C (internal member); Madura, Kiran (internal member); Jin, Shengkan (Victor) (internal member); Stock, Ann M (outside member); Rutgers University; School of Graduate Studies
Date Created2018
Other Date2018-05 (degree)
SubjectPharmacology, Cellular and Molecular, TRP channels
Extent1 online resource (ix, 128 p. : ill.)
DescriptionAs a member of the transient receptor potential ion channel subfamily, TRPM7 is a remarkable ion channel in possession of its own functional kinase domain. TRPM7 is ubiquitously expressed and permeable to divalent cations, allowing Mg2+, Ca2+, and trace metals ions such as Zn2+ to constitute the channel’s characteristic small inward current. The channel’s functional kinase domain is located at the protein’s cytosolic COOH terminus, placing TRPM7 also into a family of serine/threonine-phosphorylating alpha-kinases. It is not intuitively clear why a channel is covalently linked to a kinase, especially as it has been found that the kinase activity of TRPM7 is not required for channel gating. Previous studies have shown that TRPM7 is autophosphorylated, and yet the functional outcome of this autophosphorylation remain unknown. Motivated to understand the impact of phosphorylation on the function and regulation of this channel-kinase, I performed a comprehensive phosphoproteomic analysis of TRPM7 by mass spectrometry to identify the major in vivo phosphorylation sites on TRPM7. The results of the mass spectrometry study uncovered potential mechanisms by which the catalytic activity of TRPM7 kinase is regulated through autophosphorylation. My experiments also revealed a significant role of TRPM7’s kinase activity in regulating the posttranslational processing of TRPM7. Utilizing the TRPM7-K1646R kinase-inactive mutant, I discovered that TRPM7 kinase inactivation leads to faster protein degradation and intracellular retention of the channel in polarized epithelial cells compared to the wildtype protein. Mutational analysis of TRPM7 autophosphorylation sites further revealed a role for S1360 as a key residue mediating both protein stability and intracellular trafficking of TRPM7. In addition, I discovered that the intrinsic kinase activity of TRPM7 mediates the interaction of the channel with the signaling protein 14-3-3θ, whose binding sites on TRPM7 also contribute to the regulation of TRPM7 trafficking. Overall, these findings expand our knowledge of the in vivo phosphorylation profile of TRPM7 and, more importantly, increase our understanding of the significance of TRPM7’s kinase for functional regulation of the channel.
NotePh.D.
NoteIncludes bibliographical references
Noteby Na Cai
Genretheses, ETD doctoral
Persistent URLhttps://doi.org/doi:10.7282/T3FX7DWQ
Languageeng
CollectionSchool of Graduate Studies Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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