The calcium-calmodulin-dependent protein kinase (CaMK) subfamily of protein kinases regulate an array of cellular processes, including cell growth, gene transcription and protein translation. Dysregulation of these kinases plays a key underlying role in the pathogenesis of human diseases, particularly prostate cancer, of which therapies remain suboptimal and largely palliative in nature. The protein kinase PSKH1 is a member of the CaMK family and was shown using kinome-wide RNAi knockdown screen to be a major driver of prostate cancer progression. PSKH1 has been labelled a 'dark kinase' as very little is known about its structure, regulation and function.
Our functional studies have revealed that PSKH1 autophosphorylates, putatively on its activation loop, and that this drives activation of the protein kinase. Interestingly, unlike other CaMK family members which are prototypically regulated by the high-affinity Ca2+-decoding protein calmodulin (CaM), PSKH1 activity is attenuated by a novel family of low-affinity Ca2+-binding proteins. These CREC-family proteins, identified by TurboID/mass spectrometry, constitute a novel and understudied family of Ca2+-binding proteins whose function currently remains largely undefined . We aim to delineate the CREC-binding domain (CBD) by site-directed mutagenesis and chemical cross-linking mass spectrometry and will present our latest findings.
In conclusion, our data have revealed critical new insights into the regulation of the dark kinase PSKH1, a top-6 candidate driver of prostate cancer progression. Additionally, these data will provide a framework to enable the identification of other protein kinases in the human kinome that are potentially regulated by alternative Ca2+-binding proteins.