No abstract

Kindlin‐2 is engaged in tumor progression. However, the mechanism accounting for Kindlin‐2 regulation in tumor cells remained largely unknown. Here, we report a regulatory loop between Kindlin‐2 and GLI1, an effector of Hedgehog signaling pathway. We show that Kindlin‐2 is transcriptionally downregulated via GLI1 occupancy on the Kindlin‐2 promoter. Adversely, we found that Kindlin‐2 promotes GLI1 expression through a mechanism involving GSK3β inactivation and is independent of Smoothened. Functionally, knockdown of Kindlin‐2 cooperates with cyclopamine, a Smoothened antagonist, to decrease the viability of prostate cancer cells. Taken together, targeting the Kindlin‐2–GLI1 feedback loop may facilitate the killing of prostate cancer cells.

Kindlin proteins represent a newly discovered family of evolutionarily conserved FERM domain-containing proteins. This family includes three highly conserved proteins: Kindlin-1, Kindlin-2 and Kindlin-3. All three Kindlin proteins are associated with focal adhesions and are involved in integrin activation. The FERM domain of each Kindlin is bipartite and plays a key role in integrin activation. We herein explore for the first time the evolutionary history of these proteins. The phylogeny of the Kindlins suggests a single ancestral Kindlin protein present in even the earliest metazoan ie, hydra. This protein then underwent duplication events in insects and also experienced genome duplication in vertebrates, leading to the Kindlin family. A comparative study of the Kindlin paralogs showed that Kindlin-2 is the slowest evolving protein among the three family members. The analysis of synonymous and non-synonymous substitutions in orthologous Kindlin sequences in different species showed that all three Kindlins have been evolving under the influence of purifying selection. The expression pattern of Kindlins along with phylogenetic studies supports the subfunctionalization model of gene duplication.

Kindlin-2 is a recently identified FERM and PH domain containing integrin interacting protein. Kindlin-2 is ubiquitously expressed in normal tissues. So far, much effort has been spent exploring the functional aspects of Kindlin-2. However, the transcriptional regulation of Kindlin-2 has not yet been investigated. In this study we identified and functionally characterized the promoter of the human Kindlin-2 gene. We show that the core promoter of Kindlin-2 is a 39 base pair long GC rich fragment located −122/-83 upstream of the Kindlin-2 transcription start site. Functional characterization of this core promoter region by both in silico as well as in vitro/in vivo analysis shows that the transcription factor SP1 plays an important role in regulation of Kindlin-2 expression.