Plus-end tracking proteins, CLASPs, and a viral Akt mimic regulate herpesvirus-induced stable microtubule formation and virus spread.

Although microtubules (MTs) frequently form highly dynamic networks, subsets of MTs become stabilized in response to environmental cues and function as specialized tracks for vesicle and macromolecular trafficking. MT stabilization is controlled by specialized plus-end tracking proteins (+TIPs) whose accumulation at the MT ends is facilitated by the end-binding protein, EB1, and regulated by various signaling pathways. As cargoes themselves, viruses are dependent on MTs for their intracellular movement. Although many viruses affect MT organization, the potential contribution of MT stabilization by +TIPs to infection remains unknown. Here we show that early in infection of primary human fibroblasts, herpes simplex virus type 1 (HSV-1) disrupts the centrosome, the primary MT organizing center in many cell types. As infection progresses HSV-1 induces the formation of stable MT subsets through inactivation of glycogen synthase kinase 3beta by the viral Ser/Thr kinase, Us3. Stable MT formation is reduced in cells infected with Us3 mutants and those stable MTs that form cluster around the trans-Golgi network. Downstream of glycogen synthase kinase 3beta, cytoplasmic linker-associated proteins (CLASPs), specialized host +TIPs that control MT formation at the trans-Golgi network and cortical capture, are specifically required for virus-induced MT stabilization and HSV-1 spread. Our findings demonstrate the biological importance of +TIPs to viral infection and suggest that HSV-1 has evolved to exploit the trans-Golgi network as an alternate MT organizing center to facilitate virus spread.