# Novel Roles for Phosphoinositide Signaling in alpha-Granule Biogenesis

> **NIH NIH P01** · UNIVERSITY OF PENNSYLVANIA · 2022 · $512,710

## Abstract

Phosphorylated phosphatidylinositols (phosphoinositides) are a type of membrane bound
phospholipid that impact multiple diverse processes required for megakaryopoiesis and the
activation of platelets. We have recently published in Developmental Cell that phosphoinositides
in neuronal cells initiate intracellular trafficking by recruiting effector proteins such as GOLPH3
that are involved in vesicular fusion and budding of plasma membranes during Golgi biogenesis.
Since megakaryocyte α-granules are derived from the trans-Golgi network and Multi-Vesicular
Bodies, I hypothesize that phosphoinositide signaling is necessary for the intracellular trafficking
required for the biogenesis of α-granules. PhosphatidylInositol Transfer Proteins (PITPs) are
members of a small protein family that bind and transfer phosphoinositide monomers from one
cellular compartment to another and thereby enable phosphoinositide synthesis. We have made
the unexpected observation that the two predominant PITP isoforms found within
megakaryocytes, PITPα and PITPβ play previously unrecognized but essential roles in the
trafficking of cargo from the Multi-Vesicular Body to α-granules. Loss of PITP-mediated
phosphoinositide synthesis produces morphologic defects similar to what is seen in humans with
Gray Platelet Syndrome. The overall hypothesis of this Proposal is that phosphoinositide signaling
mediated by PITPs is necessary for the membrane dynamics and protein trafficking required for
the biogenesis and maintenance of megakaryocyte α-granules. In Aim 1 of the Project, we will
rigorously analyze the discrete biochemical properties of individual PITP isoforms in
megakaryocytes. Our preliminary data shows that the two PITP isoforms control phosphoinositide
signaling through biochemically distinct mechanisms. In Aim 2, we will determine how
phosphoinositide signaling contributes to alpha granule biogenesis and function. In conjunction
with Project 2, we will test the hypothesis that phosphoinositide synthesis within discrete
microdomains of megakaryocytes and platelets regulates effector proteins such as NBEAL2 (the
mutated protein responsible for the Gray Platelet Syndrome). This signaling cascade modulates
NBEAL2’s ability to mediate membrane dynamics and protein trafficking. We will also analyze in
detail the functional roles of α- granules with ex vivo rheologic and ultramicroscopy studies that
will be performed with Project 2, in vivo thrombosis studies with Project 3, and in vivo inflammation
studies with Project 4.

## Key facts

- **NIH application ID:** 10434809
- **Project number:** 5P01HL146373-03
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** CHARLES S. ABRAMS
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $512,710
- **Award type:** 5
- **Project period:** 2020-05-10 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10434809

## Citation

> US National Institutes of Health, RePORTER application 10434809, Novel Roles for Phosphoinositide Signaling in alpha-Granule Biogenesis (5P01HL146373-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10434809. Licensed CC0.

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