# Molecular Mechanisms Regulating Epithelial Cell Apical Polarity and Ciliogenesis

> **NIH NIH R01** · UNIVERSITY OF COLORADO DENVER · 2024 · $518,748

## Abstract

The primary cilium is a sensory organelle, found on most types of cells in vertebrates, which is required
for many of the key cellular signaling pathways. Mutations in genes involved in primary cilia formation
and function produce genetic disorders termed ciliopathies, affecting multiple organ systems. Renal
disease is a prominent feature of many ciliopathies, as defects in the primary cilia of the polarized renal
epithelial cells lead to variety of pathologies, including development of kidney cysts and loss of kidney
function. Despite the importance of apical cilia in kidney function, we still understand little about the
molecular machinery governing apical cilia formation in polarized renal epithelia. Our work during
previous funding cycle identified Rab19 as an important coordinator between cilia formation and epithelia
polarization. We have shown that Rab19 is present at the ciliated centrosome (also known as basal
body) where it regulates several stages of cilia formation, including the docking of the basal body at the
apical plasma membrane, as well as extension of ciliary axoneme.
 Despite advances in our understanding of the mechanisms mediating cilia formation in polarized
epithelial cells, many questions remain. How do epithelial cells coordinate polarization and formation of
apical structures such as cilia? How does Rab19 regulate apical cilia formation? Finally, how cilia
formation and function is disrupted in renal disorders such as polycystic kidney disease (PKD)? To start
addressing these pivotal questions we used proteomic analysis to identify TTLL12 as a Rab19-
interacting protein. Importantly, we also have shown that TTLL12 is required for cilia formation in
polarized renal epithelia, while having little effect on ciliation in non-polarized cells. TTLL12 belongs to a
family of tubulin tyrosine ligase like (TTLL) proteins. TTLL family proteins mediate secondary modification
of - and -tubulin by catalyzing tyrosination, glutamylation, or glycylation. These secondary
modifications comprise so called “tubulin code”, that affects microtubule stability, polymerization and
function. Interestingly, the enzymatic activity of TTLL12 remained unclear since it was shown to have
little effect on tubulin tyrosination, glutamylation, and glycylation. Our recent studies suggest that TTLL12
may be tubulin-specific methylase, and that tubulin methylation may play and important role in regulating
microtubule dynamics. Thus, based on our studies, we hypothesize that: Rab19-TTLL12 complex
regulates apical cilia formation and function in polarized renal epithelial cells, possibly by
mediating tubulin methylation. To test this hypothesis in vitro and in vivo we will first determine
the role of TTLL12 in regulating microtubule dynamics and stability (aim#1). Additionally, we will
determine the role of Rab19 and TTLL12 during apical cilia formation in renal polarized epithelial cells in
vitro and in vivo (aim#2).

## Key facts

- **NIH application ID:** 10898433
- **Project number:** 2R01DK064380-20
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Rytis Prekeris
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $518,748
- **Award type:** 2
- **Project period:** 2004-01-15 → 2028-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10898433

## Citation

> US National Institutes of Health, RePORTER application 10898433, Molecular Mechanisms Regulating Epithelial Cell Apical Polarity and Ciliogenesis (2R01DK064380-20). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10898433. Licensed CC0.

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