Transient concentration of a γ‐tubulin‐related protein with a pericentrin‐related protein in the formation of basal bodies and flagella during the differentiation of Naegleria gruberi

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Abstract
The distribution of two proteins in Naegleria gruberi, N‐γTRP (Naegleria γ‐tubulin‐related protein) and N‐PRP (Naegleria pericentrin‐related protein), was examined during the de novo formation of basal bodies and flagella that occurs during the differentiation of N. gruberi. After the initiation of differentiation, N‐γTRP and N‐PRP began to concentrate at the same site within cells. The percentage of cells with a concentrated region of N‐γTRP and N‐PRP was maximal (68%) at 40 min when the synthesis of tubulin had just started but no assembled microtubules were visible. When concentrated tubulin became visible (60 min), the region of concentrated N‐γTRP and N‐PRP was co‐localized with the tubulin spot and then flagella began to elongate from the region of concentrated tubulin. When cells had elongated flagella, the concentrated N‐γTRP and N‐PRP were translocated to the opposite end of the flagellated cells and disappeared. The transient concentration of N‐γTRP coincided with the transient formation of an F‐actin spot at which N‐γTRP and α‐tubulin mRNA were co‐localized. The concentration of N‐γTRP and formation of the F‐actin spot occurred without the formation of microtubules but were inhibited by cytochalasin D. These observations suggest that the regional concentration of N‐γTRP and N‐PRP is mediated by actin filaments and might provide a site of microtubule nucleation for the assembly of newly synthesized tubulins into basal bodies and flagella. Cell Motil. Cytoskeleton 52:66–81, 2002.