BME PhD Preliminary Exam Announcement for Agnes Doszpoly (T. Kinzer-Ursem, advisor)

Everyone is invited to attend the public presentation beginning at 10:00am.

Title:  Comparative Analysis of Ca²⁺- dependent CaMKII/Tiam1 Interactions with Actin in Dendritic Spines and Mammalian Eggs

Date: April 19, 2024

Time: 10:00am

Location: ABE 1164 and Zoom

Zoom link:
https://purdue-edu.zoom.us/j/92672593549
Meeting ID: 926 7259 3549

Committee:

Tamara L. Kinzer-Ursem, PhD (Chair)

Janice Evans, PhD

Deva Chan, PhD

Karin Ejendal, PhD

Abstract:

Calcium (Ca²⁺) signaling is a fundamental element of cellular life, being involved in key intracellular signaling pathways that are known for maintaining homeostasis.  It plays crucial roles in numerous cellular processes, including muscle contraction, neurotransmitter release, cell growth and differentiation. Despite the vast diversity of life forms, many key components of these pathways are highly conserved throughout evolution, including actin cytoskeletal remodeling.  Here, we investigate two systems in which Ca²⁺ signaling plays a critical role in developmental biology: (1) hippocampal dendritic spines, where spine morphology dynamics underlie the establishment of synaptic plasticity (SP) and (2) mammalian oocytes, where Ca²⁺- signaling plays a critical role in the egg-to-embryo transition, a developmental event known as “egg activation”.  In both systems, a key Ca²⁺-binding protein is Ca²⁺/CaM-dependent kinase II (CaMKII), a protein directly involved with cytoskeletal actin dynamics.  Through these properties, CaMKII indirectly regulates actin by phosphorylating T-cell lymphoma invasion and metastasis 1 (Tiam1), a Rac1 guanine nucleotide exchange factor (GEF).  In neurons, this signaling pathway has been studied to a certain extent; however, in the context of Ca²⁺- dependent spatial and temporal dynamics, little is known about the CaMKII/Tiam1 complex in dendritic spines and how their relative locations affect actin remodeling.  In mammalian eggs, CaMKII drives various egg activation events; however, the CaMKII/Tiam1 complex hasn’t been studied yet in this system, yet alone discovered whether or not this complex even exists or has actin remodeling capabilities.  The work proposed here aims to perform a comparative analysis in both biological systems of the CaMKII/Tiam1 Ca²⁺- dependent actin remodeling pathway and test the hypothesis that Ca²⁺ -dependent CaMKII/Tiam1 signaling increases structural actin remodeling in dendritic spines and fertilized mammalian eggs, tested through two specific aims: (1) quantify changes in CaMKII/Tiam1 spatial and temporal dynamics and actin remodeling under varying Ca²⁺ and CaMKII/Tiam1 perturbations in hippocampal dendritic spines, and (2) quantify changes in CaMKII/Tiam1 spatial and temporal dynamics and actin remodeling under varying Ca²⁺ and CaMKII/Tiam1 perturbations in mammalian eggs.  Through perturbations in intracellular [Ca²⁺] levels, CaMKII and Tiam1 protein expressions, the resulting actin remodeling will be quantified via immunofluorescence post hoc image analysis for dendritic spine morphology changes and establishment of membrane block to polyspermy in oocytes.  Results from both aims will be compared and assessed for conserved Ca²⁺ actin remodeling mechanisms.