Epidermal growth factor receptor levels are reduced in mice with targeted disruption of the protein kinase A catalytic subunit

Dual data and motif clustering improves the modeling and interpretation of phosphoproteomic data

Cell signaling is orchestrated in part through a network of protein kinases and phosphatases. Dysregulation of kinase signaling is widespread in diseases such as cancer and is readily targetable through inhibitors. Mass spectrometry-based analysis can provide a global view of kinase regulation, but mining these data is complicated by its stochastic coverage of the proteome, measurement of substrates rather than kinases, and the scale of the data. Here, we implement a dual data and motif clustering (DDMC) strategy that simultaneously clusters peptides into similarly regulated groups based on their variation and their sequence profile. We show that this can help to identify putative upstream kinases and supply more robust clustering. We apply this clustering to clinical proteomic profiling of lung cancer and identify conserved proteomic signatures of tumorigenicity, genetic mutations, and immune infiltration. We propose that DDMC provides a general and flexible clustering strategy for the analysis of phosphoproteomic data.

Compartmentalized Signaling in Aging and Neurodegeneration

The cyclic AMP (cAMP) signalling cascade is necessary for cell homeostasis and plays important roles in many processes. This is particularly relevant during ageing and age-related diseases, where drastic changes, generally decreases, in cAMP levels have been associated with the progressive decline in overall cell function and, eventually, the loss of cellular integrity. The functional relevance of reduced cAMP is clearly supported by the finding that increases in cAMP levels can reverse some of the effects of ageing. Nevertheless, despite these observations, the molecular mechanisms underlying the dysregulation of cAMP signalling in ageing are not well understood. Compartmentalization is widely accepted as the modality through which cAMP achieves its functional specificity; therefore, it is important to understand whether and how this mechanism is affected during ageing and to define which is its contribution to this process. Several animal models demonstrate the importance of specific cAMP signalling components in ageing, however, how age-related changes in each of these elements affect the compartmentalization of the cAMP pathway is largely unknown. In this review, we explore the connection of single components of the cAMP signalling cascade to ageing and age-related diseases whilst elaborating the literature in the context of cAMP signalling compartmentalization.

Mice lacking the Cβ subunit of PKA are resistant to angiotensin II-induced cardiac hypertrophy and dysfunction

BACKGROUND

PKA is a ubiquitous, multi-subunit cellular kinase that regulates a number of different physiological responses in response to cAMP, including metabolism, cell division, and cardiac function. Numerous studies have implicated altered PKA signaling in cardiac dysfunction. Recently, it has been shown that mice lacking the catalytic β subunit of PKA (PKA Cβ) are protected from age-related problems such as weight gain and enlarged livers, and we hypothesized that these mice might also be resistant to cardiomyopathy.

FINDINGS

Angiotensin II (ang II) induced hypertension in both PKA Cβ null mice and their WT littermates. However, PKA Cβ null mice were resistant to a number of ang II-induced, cardiopathological effects observed in the WT mice, including hypertrophy, decreased diastolic performance, and enlarged left atria.

CONCLUSION

The Cβ subunit of PKA plays an important role in angiotensin-induced cardiac dysfunction. The Cβ null mouse highlights the potential of the PKA Cβ subunit as a pharmaceutical target for hypertrophic cardiac disease.

Activated cAMP response element binding protein is overexpressed in human mesotheliomas and inhibits apoptosis

Little is known about the cellular mechanisms contributing to the development and chemoresistance of malignant mesothelioma (MM), an aggressive asbestos-associated tumor. A human mesothelial cell line (LP9/TERT-1) and isolated human pleural mesothelial cells showed rapid and protracted asbestos-induced cAMP response element binding protein (CREB1) phosphorylation, which was inhibited in LP9/TERT-1 cells by small molecule inhibitors of epidermal growth factor receptor phosphorylation and protein kinase A. Asbestos increased expression of several CREB target genes (c-FOS, EGR-1, MKP1, BCL2, and MMP13) and apoptosis, which was enhanced using small interfering CREB. Human MM tissue arrays showed elevated endogenous levels of phosphorylated nuclear CREB1 as compared with reactive mesothelial hyperplasias and normal lung tissue. Significantly increased phosphorylated CREB1 and mRNA levels of BCL2, c-FOS, MMP9, and MMP13 were also observed in MM cells in vitro, which were further augmented after addition of Doxorubicin (Dox). Small interfering CREB inhibited migration of MMs, increased apoptosis by Dox, and decreased BCL2 and BCL-xL expression, suggesting a role for these molecules in CREB-induced MM survival. These data indicate that CREB1 and its target genes are up-regulated in asbestos-exposed human mesothelial cells through an epidermal growth factor receptor/protein kinase A pathway. Since activated CREB1 also is increased endogenously in human MM and modifies migration and resistance to Dox-induced apoptosis, inhibition of CREB1 may be a new strategy for MM therapy.