FAK-targeting PROTAC as a chemical tool for the investigation of non-enzymatic FAK function in mice

FAK-targeting PROTAC as a chemical tool for the investigation of non-enzymatic FAK function in mice Dear Editor, Animal models, most commonly mice, that lack a protein of interest play an important role in phenotypic and functional studies of a target gene, allowing researchers to answer various biological questions (Chaible et al., 2010).At present, a variety of tools act at the DNA or RNA level to enable researchers to model gene function (and thus protein) deficiency, including nucleic acid-based RNA interference (Elbashir et al., 2001), antisense oligonucleotides (Schoch and Miller, 2017), and genome editing-based CRISPR-Cas9 (Doudna and Charpentier, 2014) strategies.However, challenges remain.RNA and DNA-based technologies lack exquisite temporal control of the target gene at specified time points in an organism's development, and they fail to realize acute and reversible target gene function (Chan, 2013).These shortcomings have garnered widespread concern in both fundamental research and drug development.Furthermore, gene knockout will often lead to embryonic lethality, precluding the study of post-embryonic pathophysiological functions of target genes and proteins of interest (Dhanjal et al., 2017).Proteolysis targeting chimera (PROTAC) is a novel chemical knockdown technology for the post-translational study of proteins of interest.PROTACs are hetero-bifunctional small molecules, which can drive E3 ubiquitin ligase to bind with the target protein, resulting in ubiquitination of the target protein and consequent proteasome-mediated degradation (Raina and Crews, 2010) (Fig. 1A).Unlike classic inhibitors, PROTAC eliminates rather than inhibits both enzymatic and non-enzymatic protein functions.Furthermore, unlike nucleic acid (e.g., siRNA) and genome editing-based (e.g., CRISPR-Cas9) strategies (Cong et al., 2013;Deng et al., 2014), the small molecule-based PRO-TAC approach is capable of degrading target proteins without requiring any genetic manipulation, guaranteeing the integrity and stability of the genome, which especially suitable for knockdown of embryonic lethal protein.Thus, PROTACs offer significantly broader therapeutic applicability than DNA or RNA-targeting strategies for protein knockdown in vivo.