Biology subjects

Brownlee, C. W.

Publications and source records attributed to Brownlee, C. W..

4 recordsLinked to original sources

bioRxiv2026

Palmitoylated importin α recruits PKCε to the plasma membrane to drive breast cancer cell motility

Importin is a nuclear transport factor which canonically has a role in binding and shuttling NLS-containing proteins from the cytoplasm into the nucleus. Recently, it has been shown that when palmitoylated by specific palmitoyl acyl transferases, importin can partition to the plasma membrane where its roles remain widely unknown. Patients with breast cancer displaying increased importin expression have advanced tumor size, poor tumor differentiation, and reduced overall and recurrence-free survival. In this study, we use palmitoylation altering pharmacological agents to demonstrate that membrane bound palmitoylated importin enhances breast cancer cell motility through binding and tethering the serine/threonine kinase PKC{varepsilon} to the plasma membrane.

cancer biology↗

bioRxiv2025

A Role for Importin α in Ciliogenesis and Cilia Length Regulation during Nephrogenesis

Cilia are evolutionary conserved microtubule-based organelles involved in many biological processes. Motile cilia facilitate fluid flow, while primary cilia transduce developmental and growth signals. Defects in cilia structure or function can lead to a spectrum of ciliopathies. Ciliogenesis and length regulation depend on protein transport to the ciliary base, but the molecular mechanisms remain unclear. We demonstrate that the nuclear transport protein, importin , when membrane-localized via palmitoylation, or non-palmitoylated in the cytoplasm, localizes to the base or lumen of primary and motile cilia. There we find it is required to initiate ciliogenesis and maintain proper cilia length. We found importin binds Cep164, Cep78, and Arl13b, proteins essential for ciliogenesis and length maintenance. Disrupting importin palmitoylation in Xenopus laevis lead to abnormal kidney morphology and reduced renal primary cilia. These findings reveal a novel pathway through which importin contributes to ciliogenesis and advance understanding of ciliopathy etiology.

cell biology↗

bioRxiv2024

Palmitoylated Importin α Regulates Mitotic Spindle Orientation Through Interaction with NuMA

Regulation of cell division orientation is a fundamental process critical to differentiation and tissue homeostasis. Microtubules emanating from the mitotic spindle pole bind a conserved complex of proteins at the cell cortex which orients the spindle and ultimately the cell division plane. Control of spindle orientation is of particular importance in developing tissues, such as the developing brain. Misorientation of the mitotic spindle and thus subsequent division plane misalignment can contribute to improper segregation of cell fate determinants in developing neuroblasts, leading to a rare neurological disorder known as microcephaly. We demonstrate that the nuclear transport protein importin , when palmitoylated, plays a critical role in mitotic spindle orientation through localizing factors, such as NuMA, to the cell cortex. We also observe craniofacial developmental defects in Xenopus laevis when importin palmitoylation is abrogated, including smaller head and brains, a hallmark of spindle misorientation and microcephaly. These findings characterize not only a role for importin in spindle orientation, but also a broader role for importin palmitoylation which has significance for many cellular processes.

cell biology↗

bioRxiv2017

An ordered pattern of Ana2 phosphorylation by Plk4 is required for centriole assembly

Polo-like kinase 4 (Plk4) initiates an early step in centriole assembly by phosphorylating Ana2/STIL, a structural component of the procentriole. Here, we show that Plk4 binding to the central coiled-coil (CC) of Ana2 is a conserved event, involving Polo-box 3 and a previously unidentified putative CC located adjacent to the kinase domain. Ana2 binding stimulates Plk4 kinase activity in vitro, and, in turn, is phosphorylated along its length. Previous studies showed that Plk4 phosphorylates the C-terminal STAN domain of Ana2/STIL, triggering binding and recruitment of the cartwheel protein Sas6 to the procentriole assembly site. However, the physiological relevance of N-terminal phosphorylation was unknown. We found that Plk4 first phosphorylates the extreme N-terminus of Ana2 which is critical for subsequent STAN domain modification. Phosphorylation of the central region then breaks the Plk4-Ana2 interaction. This phosphorylation pattern is important for centriole assembly and integrity because replacement of endogenous Ana2 with phospho-Ana2 mutants disrupts distinct steps in Ana2 function and inhibits centriole duplication.

cell biology↗