Regulation of Integrin Activation and Migration in Fibroblasts

Student thesis: Doctoral ThesisDoctor of Philosophy


Cell adhesion and migration is essential for normal tissue organisation and
function and dysregulation of these processes is involved in a number of
different diseases. Focal adhesions are the major sites of adhesion to the
extracellular matrix in migrating cells and integrins are a major component
of these structures. Integrins are heterodimeric transmembrane receptors
that undergo cycles of activation and inactivation at the plasma membrane
to control assembly of focal adhesions. Integrins can be activated in two
different ways; outside-in activation by binding to an extracellular ligand, or
inside-out activation though the binding of cytoplasmic proteins to the
integrin cytoplasmic tail. Talin and kindlin proteins are the two known
families of activators of integrins, and act through binding to the
cytoplasmic tail on the integrin beta subunit. Both kindlins and talin contain
phospholipid-binding domains and have been shown biochemically to be
able to bind to PIP2 or PIP3. The aim of this study is to characterize the
recruitment of talin and kindlins to integrins and their individual roles in the
sequence of receptor activation. The role of PIP2 and PIP3 in regulating
the recruitment of integrin activators to adhesion sites and the role of each
of these protein families in controlling integrin dynamics at focal adhesions
was also addressed in fibroblast cells on both 2D and 3D matrices. Data
demonstrates that kindlin2 plays the key role in fibroblast migration on 2D
and 3D matrices and that this correlates with a reduction in active integrin
levels. Moreover, live cell imaging revealed that kindlins appear at focal
adhesions prior to talin suggesting a role for these proteins in ‘priming’ the
receptor for activation by talin. Finally, these recruitment and adhesion
maturation events all depend on the balance of PIP2 local to focal adhesions. These findings shed novel light on the mechanism of integrin
activation in migrating cells.
Date of Award2014
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMadeline Parsons (Supervisor) & Simon Ameer-Beg (Supervisor)

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