ciliary protein / gene product · BEGINNER LESSON
ARL13B
ARL13B is a small GTPase protein, also called ADP-ribosylation factor-like 13B, that is enriched in primary cilia and helps maintain cilia structure and signaling.
What ARL13B is
ARL13B stands for ADP-ribosylation factor-like 13B. A GTPase is a protein that binds and hydrolyzes guanosine triphosphate (GTP), a common cellular energy-carrying molecule, and this protein is part of the ARF family in the RAS superfamily. The sources describe ARL13B as a small GTPase localized to primary cilia, which are non-motile cilia, meaning hair-like cell projections that do not beat to move fluid. In several cell types, ARL13B is important for keeping primary cilia properly formed and for placing other proteins at the ciliary membrane.
[1] Loss of a primary cilia protein ARL13B promotes TGFβ-1 induced ... [2] Unraveling the Genetic Links Between Polycystic Kidney Disease and Hypertension Through ARL13B [3] The Role of ARL13B in Mitochondrial Homeostasis in Cultured Human Corneal Endothelial Cells
What it does and how it is studied
The sources link ARL13B to cilia maintenance, intraflagellar transport (IFT; the movement of cargo along cilia needed for cilia formation and upkeep), and response to signaling pathways such as Hedgehog, Wnt, and calcium/cAMP pathways. In kidney-related analyses, ARL13B was associated with cilia morphology and with protein localization to non-motile cilia. In corneal endothelial cells, reducing ARL13B with small interfering RNA (siRNA, a short RNA molecule used to lower gene expression) changed alpha-tubulin messenger RNA, shifted aquaporin-1 (AQP1, a water-channel protein) toward the cell membrane, and increased mitochondrial oxidative phosphorylation (OXPHOS, the use of oxygen to make cellular energy). These observations show that ARL13B can affect both cilia-linked signaling and other cell functions.
[1] Loss of a primary cilia protein ARL13B promotes TGFβ-1 induced ... [2] Unraveling the Genetic Links Between Polycystic Kidney Disease and Hypertension Through ARL13B [3] The Role of ARL13B in Mitochondrial Homeostasis in Cultured Human Corneal Endothelial Cells
Mechanisms and limits of the evidence
One study found that loss of ARL13B in retinal pigment epithelial cells reduced cilia length and strengthened transforming growth factor beta 1 (TGF-β1) induced epithelial-mesenchymal transition, a change in which epithelial cells become more migratory and less tightly attached. That effect was linked to higher Smad3 signaling. In kidney analyses, altered ARL13B expression was connected to cilia dysfunction, abnormal mechanosensation, and disturbed flow sensing. However, the kidney study also notes limits: it relies on European-population data, statistical gene mapping without strong expression quantitative trait locus support, and needs experimental validation. In the corneal cell study, ARL13B knockdown did not reduce the frequency of primary cilia, showing that the effect of ARL13B change can differ by cell type and by what is being measured.
[1] Loss of a primary cilia protein ARL13B promotes TGFβ-1 induced ... [2] Unraveling the Genetic Links Between Polycystic Kidney Disease and Hypertension Through ARL13B [3] The Role of ARL13B in Mitochondrial Homeostasis in Cultured Human Corneal Endothelial Cells
SEE THE IDEA
How ARL13B acts in cells
A cilia-localized protein that helps maintain cilia structure.
Supports intraflagellar transport and protein placement at the ciliary membrane.
Can influence Hedgehog, Wnt, calcium/cAMP, and TGF-β1-related responses.
Can affect migration, epithelial-mesenchymal transition, AQP1 location, or OXPHOS depending on cell type.
ARL13B helps organize primary cilia, which changes signaling and then affects cell behavior or metabolism.
The same cilia protein can shape different downstream results in different cell types.
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Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.