# Regulation of protein transport in cilia

> **NIH NIH R01** · UNIVERSITY OF GEORGIA · 2020 · $315,000

## Abstract

Project Summary
Cilia and flagella are conserved microtubule-based cell extensions present on most cells in the
mammalian body. In addition to their role in cell locomotion and fluid transport, cilia participate in cellular
sensing and signaling. Over the past two decades, it has been established that numerous developmental
anomalies and diseases are caused by dysfunctional cilia. The goal of our work is to understand how
cells assemble and maintain cilia, which both require protein transfer between the cell body and the
organelle. A key mechanism that determines the protein content of cilia is intraflagellar transport (IFT), a
motor-based motility of large carriers (“IFT trains”) that move proteins in and out of cilia. We will use
Chlamydomonas reinhardtii as a unicellular model to determine how IFT identifies proteins destined for
the cilium and how the cells regulate the volume and timing of ciliary protein traffic. In Aim1, we will focus
on the transport of tubulin, the main structural protein of cilia and flagella. The amount of tubulin and
other axonemal proteins entering cilia on IFT trains is upregulated while cilia grow. Tubulin also enters
cilia by diffusion and we will establish the quantitative contribution of each route in cilia assembly. We will
determine if IFT54 is part of the previously characterized IFT74-IFT81 tubulin-binding module or if it
forms an independent tubulin-binding site. All three proteins interact with tubulin via their tubulin-binding
domains (TBDs). Isolated IFT complexes will be used to study if the TBDs undergo biochemical changes
related to cargo binding and cilia length. We will attempt to map the TBDs on isolated IFT particles and
we will study whether IFT particles undergo structural changes inside cilia potentially explaining the
differences in cargo binding. We expect to gain insights into how cells regulate tubulin transport, which is
critical for the timing of ciliogenesis and the regulation of ciliary length. In Aim 2, we will focus on the
transport of proteins associated to the ciliary membrane by lipidation. Such proteins are critical for the
sensory and signaling functions of cilia. Often, they enter and exit cilia to modulate signaling but the role
of IFT in this traffic is mostly unknown. In cilia of C. reinhardtii mutants in BBS proteins or Arl13b, the
patterns of membrane-associated proteins are severely affected. In humans, mutations in BBS proteins
and Arl13b result in Bardet-Biedl syndrome (BBS) and Joubert syndrome, respectively. Both mutants
show loss and abnormal accumulation of membrane-associated proteins in cilia, raising the question
whether more than one route of transport is affected. We will use in vivo imaging to determine the role of
IFT and diffusion in ciliary entry and export of proteins mislocalized in these mutants. We will test a
hypothesis that initial ciliary defects caused directly by the bbs and arl13b mutations will induce
additional biochemical defects increasingly im...

## Key facts

- **NIH application ID:** 9872171
- **Project number:** 5R01GM110413-07
- **Recipient organization:** UNIVERSITY OF GEORGIA
- **Principal Investigator:** Karl F. Lechtreck
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $315,000
- **Award type:** 5
- **Project period:** 2014-06-10 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9872171

## Citation

> US National Institutes of Health, RePORTER application 9872171, Regulation of protein transport in cilia (5R01GM110413-07). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9872171. Licensed CC0.

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