Integrin-Linked Kinase Regulates Process Extension in Oligodendrocytes via Control of Actin Cytoskeletal Dynamics

Abstract

Integrin-linked kinase (ILK) is a major structural adaptor protein governing signaling complex formation and cytoskeletal dynamics. Here, through the use of conditional knock-out mice, we demonstrate a requirement for ILK in oligodendrocyte differentiation and axonal myelination in vivo. In conjunction, ILK-deficient primary oligodendrocytes are defined by a failure in process extension and an inability to form myelin membrane upon axonal contact. Surprisingly, phosphorylation of the canonical downstream targets Akt and GSK3␤ is unaffected following ILK loss. Rather, the defects are due in part to actin cytoskeleton dysregulation with a correspondent increase in active RhoA levels. Morphological rescue is possible following Rho kinase inhibition in an oligodendrocyte subset. Furthermore, phenotypic severity correlates with environmental complexity; oligodendrocytes are severely malformed in vitro (a relatively simple environment), but undergo phenotypic recovery in the context of the whole animal. Together, our work demonstrates ILK as necessary for normal oligodendrocyte development, reinforces its role as a bridge between the actin cytoskeleton and cell membrane, and highlights the overarching compensatory capacity of oligodendrocytes in response to cellular milieu.

Jmy regulates oligodendrocyte differentiation via modulation of actin cytoskeleton dynamics

“…Control of F-actin assembly is known to play an essential role in OL differentiation and initiation of myelination (O'Meara et al, 2013;Zuchero et al, 2015) but the details of the molecular network that links actin dynamics to function in OLs are not fully characterized. With this in mind, we chose to study the recently identified multifunctional actin assembly factor Jmy, which came up in our RNA-Seq screening as an mRNA that is asymmetrically distributed in OPCs during initial extension of membrane protrusions (Figure 1c (Bhat & Zhang, 1996).…”

“…Among the most heavily regulated genes, aside from those encoding myelin proteins, are ones involved in cell cycle and motility, adhesion, and cytoskeletal remodeling. It is likely that different actin regulators have distinct roles in myelination: WASP-family verprolin-homologous protein (WAVE) and integrin-linked kinase (ILK) regulate OL differentiation and axon ensheathment (Kim et al, 2006;O'Meara et al, 2013), while the Arp2/ 3 complex, a major actin nucleator, is required for initiation of myelination in vivo (Zuchero et al, 2015), and Rho GTPases Cdc42 and Rac1 regulate myelin sheath formation (Thurnherr et al, 2006). It has been shown that myelin basic protein (MBP) triggers actin depolymerization by promoting the release of actin disassembly proteins (Zuchero et al, 2015).…”

Metabolic Vulnerability in the Neurodegenerative Disease Glaucoma

“…These estimates assume glucose diffusion to the middle of an internode quickly (see Figure 2); rat internodes average 240 μm (Ransom et al, 1991) while internode lengths in mouse ON average 110 μm (O'Meara et al, 2013). This internode length suggests glucose will readily diffuse; however, the predicted ATP shortfall in axons below 0.8 μm in diameter indicates a potential vulnerability of small axons.…”

Effects of HIV‐1 Tat on oligodendrocyte viability are mediated by CaMKIIβ–GSK3β interactions

“…In cell culture, loxP‐flanked genes can be excised by adding cell‐permeable Cre recombinase to the media (O'Meara et al . ). RT‐PCR showed that 50 nM Cre recombinase significantly decreased the mRNA level of Camk2b in mature OL cultures at 24 h (Fig.…”