PCTK1 Regulates Integrin-Dependent Spindle Orientation via Protein Kinase A Regulatory Subunit KAP0 and Myosin X

• Published in: Molecular and cellular biology 2015-04, Vol.35 (7), p.1197-1208
• Main Authors: Iwano, Sayaka, Satou, Ayaka, Matsumura, Shigeru, Sugiyama, Naoyuki, Ishihama, Yasushi, Toyoshima, Fumiko
• Format: Article
• Language: English
• Subjects: Cyclic AMP-Dependent Protein Kinases - metabolism; Cyclin-Dependent Kinases - metabolism; HeLa Cells; Humans; Integrin beta1 - metabolism; Myosins - metabolism; Protein Subunits - metabolism; Spindle Apparatus - metabolism; Spindle Apparatus - ultrastructure
• ISSN: 1098-5549; 0270-7306; 1098-5549
• DOI: 10.1128/MCB.01017-14

Integrin-dependent cell-extracellular matrix (ECM) adhesion is a determinant of spindle orientation. However, the signaling pathways that couple integrins to spindle orientation remain elusive. Here, we show that PCTAIRE-1 kinase (PCTK1), a member of the cyclin-dependent kinases (CDKs) whose function is poorly characterized, plays an essential role in this process. PCTK1 regulates spindle orientation in a kinase-dependent manner. Phosphoproteomic analysis together with an RNA interference screen revealed that PCTK1 regulates spindle orientation through phosphorylation of Ser83 on KAP0, a regulatory subunit of protein kinase A (PKA). This phosphorylation is dispensable for KAP0 dimerization and for PKA binding but is necessary for its interaction with myosin X, a regulator of spindle orientation. KAP0 binds to the FERM domain of myosin X and enhances the association of myosin X-FERM with β1 integrin. This interaction between myosin X-FERM and β1 integrin appeared to be crucial for spindle orientation control. We propose that PCTK1-KAP0-myosin X-β1 integrin is a functional module providing a link between ECM and the actin cytoskeleton in the ECM-dependent control of spindle orientation.