# Signaling Mechanisms and Cellular Functions of a Ciliopathy-Associated Protein Kinase

> **NIH NIH R01** · UNIVERSITY OF VIRGINIA · 2021 · $332,690

## Abstract

Project Summary
Ciliopathies comprise an expanding group of human disorders associated with genetic mutations causing cilia
dysfunction. Cilia can be divided into motile and non-motile (primary) forms. The primary cilium is a microtubule
(MT)-based organelle that protrudes from the apical surface of nearly every mammalian cell and plays a critical
role in chemical sensation, signal transduction, and control of various cellular functions. To date, there are still
major gaps in our knowledge about the dynamic structure and function of the primary cilium, and the
underlying molecular basis of ciliopathies. Our research proposal is focused on elucidating the molecular
mechanism by which pathogenic mutations in the human CILK1 (ciliogenesis associated kinase 1) gene cause
ciliopathies. CILK1 encodes a serine/threonine protein kinase that negatively regulates cilia length and
ciliogenesis. Three significant questions about CILK1 remain to be addressed. First, what is the identify of
CILK1 substrates that relate to its ciliopathy phenotype? Our data challenged the current view that MT-
associated motor KIF3A is the CILK1 substrate responsible for the ciliopathy phenotype by showing that
disrupting CILK1 phosphorylation of KIF3A in vivo did not reproduce CILK1 mutant phenotype. In this
continuation project, we hypothesize that CILK1 suppresses ciliogenesis by phosphorylating a novel MT-
associated ciliary protein and promoting MT disassembly. Second, how is CILK1 activity regulated in the
primary cilium? CILK1 requires phosphorylation of its MAPK-like TDY motif for full activation, but growth factors
have little stimulatory effect on its activity. Our new preliminary data shows that reducing intracellular cAMP
stimulates CILK1. We hypothesize that CILK1 activity is negatively regulated by ciliary cAMP-dependent
phosphorylation. Third, how CILK1 human disease variants impact cilia function and signaling and tissue
development? We observed human disease variants in the non-catalytic C-terminal domain (CTD) of CILK1
that retain CILK1 catalytic activity but produce a loss-of-function effect on suppression of ciliogenesis. We
hypothesize that CILK1 variants in the CTD perturb CILK1 localization and substrate recognition, thereby
compromising its ability to suppress ciliogenesis. We propose three specific aims to test these hypotheses.
Aim 1 will determine how CILK1 signals through a novel signaling pathway to control cilia length and
ciliogenesis. Aim 2 will determine how cAMP inhibits CILK1 to elongate cilia and promote ciliogenesis. Aim 3
will determine the impact of CILK1 pathogenic variants on substrate phosphorylation, cilia function, Hedgehog
signaling, and tissue development. The significance of this project derives from human ciliopathies that have
an expanding disease spectrum with devastating clinical outcomes. Our studies are innovative in using novel
genetically engineered animal and cell models to elucidate new mechanisms that control cilia funct...

## Key facts

- **NIH application ID:** 10210778
- **Project number:** 2R01GM127690-03A1
- **Recipient organization:** UNIVERSITY OF VIRGINIA
- **Principal Investigator:** Zheng Fu
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $332,690
- **Award type:** 2
- **Project period:** 2018-05-01 → 2025-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10210778

## Citation

> US National Institutes of Health, RePORTER application 10210778, Signaling Mechanisms and Cellular Functions of a Ciliopathy-Associated Protein Kinase (2R01GM127690-03A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10210778. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*