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The Department of Biomedicine

BBB Seminar: Michael Leitges

Roles of individual Protein Kinase C isoforms during tumorigenesis

Michael Leitges,
The Biotechnology Centre of Oslo, University of Oslo

The focus of the group is the analysis of the in vivo functions of Protein Kinase C (PKC). PKC comprises a protein family of at least 12 independent members, generated from 9 different genes, which in vitro using biochemical approaches behave quite similar. Thus the identification and analysis of isoform-specific functions have been a challenge for quite a while. We use the gene targeting approach in mice to generate individual PKC deficient mouse lines which can serve as a tool to identify and investigate isoform-specific PKC functions in vivo.

The basic dogma within the group was to start with a functional analysis of the mutant mouse lines by asking the question where exactly in the organism the individual PKC isoforms are expressed. We use specific tools which we have subsequently generated, such as specific RNA in situ probes, isoform-specific antibodies and reporter alleles in mice to establish individual expression profiles of PKC isoforms at a very precise level. Using this strategy we recently investigated PKC profiles in a colon cancer model in mice (APCMin) indicating that PKCalpha and PKCzeta become down-regulated during polyp formation. Based on these data we have established the appropriate mouse lines harboring the APC mutation on a PKCalpha or PKCzeta deficient background. In fact the APCMin/PKCalpha deficient mouse line develops more polyps at earlier time points which consequently lead to early death of this mutant mouse line. This defines PKCalpha as a tumor suppressor in this context. Subsequently, we were able to show that PKCalpha depletion modulates EGF receptor activity causing a more pronounced proliferative signal in intestinal epithelian cells than the APC mutation itself.

 

Host: Hans-Hermann Gerdes, Department of Biomedicine