UCLA

For many types of animal cells, migration is essential for their physiological function. Long distance crawling is required for the development of a nervous system and for the ability of macrophages to accumulate at sites of infection. In response to a wound, resident fibroblasts migrate to the wound site and promote the wound healing process. Furthermore, cancer metastasis involves the ability of cancer cells to transform their morphology and acquire an ability to migrate. A better understanding of cell migration would have implications for normal development and could yield therapies for multiple different disease states, including fibrosis, atherosclerosis, and metastasis.

Alternative polyadenylation (APA) is the process by which the same genetic locus can produce multiple transcripts ending at different polyadenylation sites. Coding sequence APA can change the length of the amino acid and can also switch the function of the protein. Proliferating cells, cancer cells, and stem cells in the early stages of mouse development and tumors tend to use proximal polyadenylation sites and commonly show rapid cell migration. Our laboratory has discovered that fibroblast migration can be regulated through polyadenylation site selection. To date, however, no studies have been performed to research how cell migration and invasion can be controlled by APA.

Reversion-inducing-cysteine-rich protein with kazal-like motifs (RECK) suppresses cell migration. Previous studies have documented a role for RECK on the cell surface in inhibiting MMP activity via its Kazal-like motifs. RECK has also been implicated in tubulin dynamics and in anterior-posterior polarity. Our lab discovered through an RNA-Seq-based screen that there are short and long RECK isoforms that are generated by coding region alternative polyadenylation.

In this dissertation, I explain how cell migration and invasion can be controlled by APA via alternative isoform expression of the RECK protein. I show that the short RECK isoform promotes cell migration and that this result is mediated by short RECK and long (canonical) RECK interaction. Furthermore, I propose that RECK APA can regulate cell migration not only through its established role of modifying matrix metalloproteinases but also via its roles in affecting tubulin post-translational modifications (PTMs). These studies provide a much more detailed and mechanistic model for the biological functions of RECK alternative isoform use.