Low Density Lipoprotein Receptor-Related Protein 1 and the Plasminogen Activators Gate Phase Shifting in the Mammalian Circadian Clock
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University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2018 To shift or not to shift: Low density lipoprotein receptor-related protein 1 and the plasminogen activators gate phase shifting in the mammalian circadian clock Joanna Marie Cooper University of Tennessee, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Recommended Citation Cooper, Joanna Marie, "To shift or not to shift: Low density lipoprotein receptor-related protein 1 and the plasminogen activators gate phase shifting in the mammalian circadian clock. " PhD diss., University of Tennessee, 2018. https://trace.tennessee.edu/utk_graddiss/4982 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Joanna Marie Cooper entitled "To shift or not to shift: Low density lipoprotein receptor-related protein 1 and the plasminogen activators gate phase shifting in the mammalian circadian clock." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Biochemistry and Cellular and Molecular Biology. Rebecca A. Prosser, Major Professor We have read this dissertation and recommend its acceptance: Jerome Baudry, Matthew A. Cooper, Cynthia B. Peterson Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To shift or not to shift: Low density lipoprotein receptor-related protein 1 and the plasminogen activators gate phase shifting in the mammalian circadian clock A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Joanna Marie Cooper May 2018 ACKNOWLEDGEMENTS Earning a PhD is not a solitary undertaking, and there are countless individuals to whom I owe many thanks for their support and encouragement along the way. First and foremost, I would like to thank my PhD mentor, Dr. Rebecca Prosser, for her guidance and support throughout the duration of my time at UTK. Thank you, Rebecca, for constantly believing in me and fostering an environment where I could grow, both as a scientist and an individual, and for never having a closed door, no matter how small or large the problem. I also would like to thank my committee members, Dr. Cynthia Peterson, Dr. Jerome Baudry, and Dr. Matthew Cooper for their support and guidance, as well as Dr. Jim Hall. A very special thank you goes to Dr. Dudley Strickland at the University of Maryland School of Medicine, who agreed to serve as an external member of my committee. Thank you for your dedication to supporting me from a distance, and for constantly advocating for my work. I also owe much to my peers. To the Prosser lab members, past and present: Dr. Beth Cantwell, Dr. Yuki Yamada, Dr. Jonathan Lindsay, and Kathryn Abrahamsson, thank for filling the lab with love and laughter. Some of my fondest grad school memories are from our times together in lab or traveling for conferences. Thank you to the graduate students throughout the department – Dr. Jessica Gullett, Andrew Stafford, Emily Stow, Lindsey Yoder, Dana Layo – and many more, who offered friendship and support throughout the years. Thank you to the many undergraduate researchers who have contributed to my time in the lab: Cody Burleson, Robert, Rachel, Ramil, Tucker, John, Amina, Jackie, Saxon – I learned something from each of you. I would also like to acknowledge those individuals from my past who helped me get to graduate school: Dr. Ben Bahr, Dr. Bob Poage, & Dr. Laurie Andolina, thank you for being wonderful mentors in my early stages – without your guidance I would have never dreamed of reaching this goal. And finally, thank you Mom and Dad. I could not have done this without your endless love, support, and encouragement. And Melissa, Matt, and Lauren, thank you for the ways you each have made me feel special and helped make the distance between us seem so small. A PhD changes a person, and it is the people around you that make the most a lasting imprint. I am humbled by the amazing support I have received from so many wonderful individuals on my path to this degree. ii ABSTRACT Here, we present data supporting low density lipoprotein receptor-related protein-1 (LRP- 1) and urokinase plasminogen activator (uPA) involvment in the suprachiasmatic nucleus (SCN), the primary mammalian circadian pacemaker. Previous work using extracellular recordings of SCN neurons in ex vivo hypothalamic slices demonstrated that tissue-type plasminogen activator (tPA) gates glutamate-induced phase shifts via plasmin-dependent maturation of brain derived neurotrophic factor (BDNF) and subsequent tropomysin receptor kinase B (TrkB) receptor activation. Here, we find first, that tPA knockout mice (tPA−/−; B6.129S2-Plattm1Mlg/J) exhibit minimal phase shifting deficits in vivo and in vitro, and that uPA compensates for the lack of tPA to enable phase shifts in these mice. Intriguingly, the data support tPA, but not uPA, acting via BDNF maturation, suggesting functional compensation achieved through differential mechanisms. Second, we find that LRP-1 also regulates SCN phase shifting. Inhibiting LRP-1 with receptor associated protein (RAP) or anti-LRP-1 antibody prevents glutamate-induced phase delays and advances in neuronal activity rhythms in vitro at ZT16 and ZT23, respectively. We then turned our attention to potential interactions between tPA and LRP-1, and through three lines of evidence demonstrate that tPA proteolytic activity is not necessary for LRP-1’s permissive effect on phase shifting: 1) RAP inhibits phase shifts in tPA-/- SCN, 2) inhibiting LRP-1 does not impact BDNF maturation, or 3) Trk receptor phosphorylation on Y680/681. Suprisingly, inhibiting LRP-1 with RAP changes N-Methyl_D-aspartic acid receptor (NMDAR) phosphorylation patterns in the SCN in vitro, by decreasing phosphorylation on S1480 of NR2B subunits. Finally, we evaluated uPA and tPA expression and proteolytic activity across the circadian day, and LRP-1 expression and phosphorylation patterns. We find evidence of circadian rhythms in tPA expression but not proteolytic activity, no rhythms in uPA expression or proteolytic activity, and potential diurnal variations in αLRP- 1 but not βLRP-1 subunits. Additionally, uPA activity and βLRP-1 expression exhibit changes that correlate with the time slices are maintained in vitro, suggesting that a response to slicing injury may occlude an accurate view of expression patterns in the SCN in vitro. Collectively, the data presented here implicate uPA and LRP-1 in the processes gating glutamate-induced phase shifts in the SCN. iii TABLE OF CONTENTS 1 Introduction ............................................................................................................. 1 1.1 Circadian Rhythms .......................................................................................... 2 1.1.1 Circadian timekeeping mechanisms and the SCN ................................... 2 1.1.2 Neuronal plasticity in the SCN – daily rhythms in neuronal responses to glutamate ................................................................................................................ 6 1.2 The Plasminogen Activators ............................................................................ 9 1.2.1 tPA regulates glutamate signaling in the brain ....................................... 10 1.2.2 uPA influences neuronal processes ....................................................... 12 1.2.3 tPA regulates glutamate-induced phase shifts ....................................... 13 1.3 Low-density lipoprotein receptor-related protein-1 ......................................... 15 1.3.1 LRP-1 introduction ................................................................................. 15 1.3.2 LRP-1 regulates neuroplasticity throughout the brain ............................. 16 1.3.3 LRP-1 overlaps with mechanisms that gate phase shifts ....................... 18 2 Urokinase-type plasminogen activator modulates mammalian circadian clock phase regulation in tissue-type plasminogen activator knockout mice ..................................... 19 2.1 Abstract ......................................................................................................... 20 2.2 Introduction ................................................................................................... 21 2.3 Materials and Methods .................................................................................. 23 2.3.1 Animals .................................................................................................. 23 2.3.2 In vivo methods ..................................................................................... 23 2.3.3 In vitro methods ..................................................................................... 24 2.3.4 Western blots ......................................................................................... 25 2.3.5 Casein-plasminogen gel zymography .................................................... 26 2.3.6 Statistical