Abstract
The remodeling capacity of microtubules (MT) is essential for their proper function. In mammals, MTs are predominantly formed at the centrosome, but can also originate from non-centrosomal sites, a process that is still poorly understood. We here show that the small heat shock protein HSPB1 plays a role in the control of non-centrosomal MT formation. The HSPB1 expression level regulates the balance between centrosomal and non-centrosomal MTs. The HSPB1 protein can be detected specifically at sites of de novo forming non-centrosomal MTs, while it is absent from the centrosomes. In addition, we show that HSPB1 binds preferentially to the lattice of newly formed MTs in vitro, suggesting that its function occurs by stabilizing MT seeds. Our findings open new avenues for the understanding of the role of HSPB1 in the development, maintenance and protection of cells with specialized non-centrosomal MT arrays.
Highlights
The small heat shock protein HSPB1 is a ubiquitously expressed molecular chaperone that besides its canonical folding function is involved in a wide range of cellular processes such as apoptosis, actin cytoskeleton regulation and cell proliferation [1]
In 2004 we found that mutations in HSPB1 cause a peripheral neuropathy called Charcot-Marie-Tooth disease (CMT) [3]
While studying the role of CMT-causing HSPB1 mutants in MT biology [5] we observed that HeLa cells overexpressing HSPB1 display a less prominent MT aster when compared to their naive, untransfected counterparts during repolymerization of the MT network
Summary
The small heat shock protein HSPB1 ( known as HSP27) is a ubiquitously expressed molecular chaperone that besides its canonical folding function is involved in a wide range of cellular processes such as apoptosis, actin cytoskeleton regulation and cell proliferation [1]. In 2004 we found that mutations in HSPB1 cause a peripheral neuropathy called Charcot-Marie-Tooth disease (CMT) [3]. We discovered that a subset of these CMT causing HSPB1 mutations leads to higher chaperone activity [4] and an increased binding of HSPB1 to tubulin and MTs [5]. This enhanced binding stabilizes the MT network in a similar fashion to what is described for other microtubule associated proteins (MAPs) [6]. We show that HSPB1 regulates the architecture of the cellular MT network by facilitating the formation of noncentrosomal MTs
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