Abstract
Profilin 1 is a crucial actin regulator, interacting with monomeric actin and several actin-binding proteins controlling actin polymerization. Recently, it has become evident that this profilin isoform associates with microtubules via formins and interferes with microtubule elongation at the cell periphery. Recruitment of microtubule-associated profilin upon extensive actin polymerizations, for example, at the cell edge, enhances microtubule growth, indicating that profilin contributes to the coordination of actin and microtubule organization. Here, we provide further evidence for the profilin-microtubule connection by demonstrating that it also functions in centrosomes where it impacts on microtubule nucleation.
Highlights
The centrosome is the major microtubule-organizing structure in eukaryotic cells and as such crucial for intracellular architecture, cell polarity, and directional migration; it has intrigued scientists for decades [1]
Recent cryo-electron microscopy revealed that the lumen of γ-tubulin ring complex (γTuRC) contains an actin-like molecule associated with both the GCPs and γ-Tbs [22, 23, 24], which appears to be important for γTuRC-dependent microtubule nucleation [23]
The fluorescence intensity emanating from the centrosome after profilin Ab staining increased 1.6 times in cells during mitosis (Fig S1A–C)
Summary
The centrosome is the major microtubule-organizing structure in eukaryotic cells and as such crucial for intracellular architecture, cell polarity, and directional migration; it has intrigued scientists for decades [1]. Several actin regulatory components such as WASH, Arp2/3, cofilin, and members of the formin family [2, 7, 14] have been found to be associated with the centrosome and likely to govern centrosome-linked actin reorganization. Examples of such activities are for instance the alteration of actin organization during synapse formation in immune cells with subsequent centrosome relocation and changes in microtubule distribution [9] and the centrosomal actin polymerization linked to spindle formation during mitosis in somatic mouse and human cells [15]. The connection between actin and γ-Tb is further emphasized by reports of the latter localizing to the actin-rich cell periphery and influencing stress fiber formation [25]
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